Eureka!: Inventors describe the moment they realised they’d created a hit

Arthur Fry, chemical engineer

The Post-it note

it was 1975, just after Christmas, and I was working at the 3M base in Maplewood, Minnesota; I was developing products for the commercial tape laboratory where the big money-maker was Magic Tape. At that time I was singing in the local church choir. I got up to sing one Sunday morning and the little piece of paper I'd used to mark my page had fallen out. During a rather dull sermon, I wondered how to make a bookmark that would stick to paper and not fall out, without tearing the paper apart. All the adhesives I knew of stuck to paper fibres stronger than paper fibres stuck to themselves.

I remembered an adhesive one of our researchers had developed some years earlier, which consisted of rather large particles that when coated on a surface would be small enough that you could get a smooth surface. I thought: What if I spread those particles out, will they stick less strongly than if pushed together? In the lab the next morning, I coated out samples of Dr Silvers' micro-spheres at different lengths and spacings.

At first the particles wouldn't stay put, they half-transferred to whatever you stuck them to, but I understood how to make a primer that would stick to paper. I had a bookmark that worked.

I gave samples to my secretary, librarian, business managers, and asked them to tell me how they got on. Afterwards, I quizzed them: how did it work? What did you stick them to? They were writing notes, reminders, thank-yous. These were more than just bookmarks. I made them by hand, in every colour. The market research teams were telling me these weren't viable products, but people were trudging through knee-deep snow to my lab to get them. Now Post-it notes turn over more than $1 billion a year.

When you're trying to create something totally new you run into one barrier after another: how to make it into pad form? How to measure the adhesive in such small quantities? How to apply the glue with such precision?

All of these questions required a creative solution; I had to invent new equipment to make them. It was a whole string of eureka moments. You can tell the innovators by their determination and stubbornness; we're all addicted to the adrenaline rush you get with that moment of revelation. More than 25 million Post-it products are sold in the UK every year

Mary Quant, fashion designer

The miniskirt

like most little girls, I used to be sent to ballet classes. One day I could hear exciting music coming from next door, and when I peeked through the glass I saw a tap-dancing class taking place, and in the middle of the room, a girl a couple of years older than me who was the vision of everything I wanted to be. She was wearing a short pleated skirt about 10 inches long, with a skinny black sweater, black tights and a bob haircut. What struck me was how the whole outfit focused on what she wore on her feet: a pair of white ankle socks, and a pair of black patent tap shoes with ankles straps. They exaggerated the whole look. I realised at that moment that when you move the focus around, everything gets much more interesting.

Everything about this girl made her infinitely more interesting looking than I had ever looked. From that day on I was stuck with this lovely vision of legs and ankles. I used to inherit very proper clothes from my cousin, which were girly and didn't make much impact. From that day on, the image of that girl stayed with me, I started trying to make my own clothes, cutting up bedspreads. I used to start rearranging my school uniform, hitching up my skirt to be more exciting-looking.

Women's clothes had always been so inhibiting. The miniskirt started to represent a certain freedom: in it you could move, run to catch the bus, leap about, and most importantly, you could dance. And legs are wonderful, aren't they? Nice to look at and nice to use. The miniskirt played on that. If something looks terrific and is practical there's every reason for people to love it. It's as simple as that. The miniskirt, popularised by Mary Quant in the 1960s, epitomised the fashion revolution of the era and endures to this day

Friedhelm Hillebrand, project manager

The SMS message

it was a product of its time. I was in Bonn, Germany, in 1984, working as the project manager for Deutsche Telekom. We were working with other telecoms companies on the standardisation of the mobile systems across Europe, and as part of this much bigger assignment, I conceived the idea of the Short Message Service, which would become the SMS text message as we know it today. It was a way of using your telephone keypad to create and send messages, but because of the channels it used, the message had to be limited to 160 characters. That limitation also set the blueprint for what is now the de facto length for communication in social media.

The concept was straightforward, but the big question was, would it be useful to customers? For an idea to be financially viable in this business, it has to appeal to a huge audience. No other communication service at that time – letter, fax, telephone – had a limitation of message length. Would a service that was limited to three lines on a typewriter be of use to anyone? I had serious doubts. I discussed it with colleagues – they had doubts, too.

I set about looking at what else was working well. In the professional area, telex messages were popular at that time – and they were very short – as was the fax, and with this it seemed to be the norm to write just two or three sentences. I counted the words on the back of postcards, too, which gave me further confidence. Finally, I started typing some messages to get a feeling of what it was like. It wasn't concrete evidence, but it was enough. To bring the SMS to reality was a group effort with the contributions of many colleagues.

At the time, it was impossible to understand the potential impact of what I'd conceived. At that time, of course, we had no idea how huge the telecoms market would become. Today, the SMS message has so many positive effects. But I find people terminating their romantic relations with a short message an impertinent use of my idea.

With 2.4 billion active users, the SMS is now the most widely-used data application in the world

Steve McCurry, photographer

The Afghan Girl

it was a fleeting moment, one I knew I had to capture. I was on an assignment for National Geographic photographing displaced Afghans in a refugee camp in Pakistan, just outside Peshawar. I stumbled upon a tent which was being used as a girls' school. It was chaos, then there, across the room I saw that girl – those eyes – I knew at once I'd found the one. Sometimes as a photographer, on some sort of intuitive level you can feel the power of what is in front of you. This girl was very pretty, but it was more than that. It was clear from her face that she'd experienced more than you or I could imagine. There was no ambiguity that this was something quite extraordinary, and I didn't have much time.

I was shooting with a tripod on Kodachrome 64, a transparency slide film, which is slow. I was worried if I approached the girl straight away she might say no, so I photographed a few of her friends first, trying to create a situation where she didn't want to be excluded. Nobody spoke English, so we used sign language to communicate. In this part of the world, classes are conducted on the floor; no tables or desks. You don't really direct people in that kind of situation, you just take what is offered.

The girl was sitting on the ground. There was an amazing light coming into the tent behind her; I positioned my camera so that it fell on her face. I tried to stay calm and focused because I knew this was a special moment and that for a minute she'd be amused by the strange man with his strange equipment, and then she'd bore and wander off. There was so much motion in the classroom, kids screaming, dust; it wasn't this sort of still, profound moment when she revealed herself.

I only had a chance to take a few exposures before she walked away. I could see the image in my mind, but I didn't know how it would have translated to film. I sent the film back to the States but I had more work to do here so I didn't see the results until a few weeks later. The magazine's photo editor and I edited the film down to two slides. I liked this picture, but he thought it was too haunting; he preferred one with her hand covering part of her face. We agreed to present both to the editor, who leapt to his feet and said: "This is our next cover!". Sometimes you just know.

Afghan Girl first appeared on the cover of 'National Geographic' in June 1985 and was later the subject of a TV documentary, 'Search for the Afghan Girl'

John Pasche, designer

The Rolling Stones logo

when you're first given a brief it's almost like being hit by a great wall of panic. At first it's a matter of scrambling around for ideas – you just have to think of something. I tend to make one idea a 'banker', and then think around it. I usually come back to the original.

Sometimes you just get a feeling about an idea. I had a very strong sense about this logo for the Rolling Stones. I'd met with Mick Jagger at his house on Cheyne Walk in west London; it was 1971. The band wanted a new logo, for letterheads and possibly a small record label they were thinking of starting up for their mates. We had a chat about the kind of things Jagger liked. He was really into Indian artefacts and had this image he found of the Indian god Kali, with his very pointed tongue sticking out of its mouth.

Subconsciously, it had become a matter of finding a symbol for the bad boys of rock'n'roll; a simple and irreverent statement of anti-establishmentarianism. Suddenly, looking at the image of Kali, that very basic concept of sticking your tongue out struck me as just the thing. I didn't say anything at first, I just told Mick, "I'll go away and have a think".

At home I spent a long time trying to find the right form for the image. It's surprising quite how difficult it is trying to draw a disembodied mouth and tongue. It was a matter of madly scrawling down ideas. I was aware it needed to be very simple so it could be reproduced in small sizes; automatically it started to take on an almost cartoon-ish look. I did loads of versions, each just slightly tweaked – some slightly more to the side, some straight-on – but, for some intangible reason, this one just worked best.

A week later, Jagger saw the final version and liked it, so much so they decided to use it for the inner bag of the Sticky Fingers album too, so I had to alter the shape to make it quite big. That was the lips' first public outing. Then T-shirts started appearing on market stalls, and it just grew. The 1970s was the advent of bands doing big tours, and with that came merchandising. The image was only meant for very limited usage, so I was only paid £50 for it – although for me, a year out of college, that seemed all right for a week's work. The V&A, which bought the original artwork for £58,000, describes it as as "one of the world's most instantly recognisable symbols of rock'n'roll"

Sue Townsend, author

Adrian Mole

one boring Sunday afternoon my son said to me: "Why don't we go to safari parks like other families?". The reason was we were too poor and had no car. Suddenly that teenage voice – self-pitying and semi-cruel, disbelieving that they could have been born to such a family – just descended on me. I sat down and started writing; without even thinking the words just came pouring out.

Adrian's family fell straight onto the page. I wrote a few months' worth of the diary without pausing for breath. It wasn't a continuous flow from one month to next, just a notebook filled with scrawlings which I kept locked in a box. When I found out it was going to be performed as a radio play, I had to go back and fill in the gaps.

Having left school at 14, I'd worked with teenage boys in a youth club and those who came to your attention were loud and needy. I knew what they were like and how they thought – I found nearly every one was sentimental about his mother, and an awful lot of them quite contemptuous of their fathers, whom they expected to be some kind of macho god. But Mole is also me.

I always say I'm not a writer, I'm a rewriter. Books aren't created in a moment, stories and characters are built over a lifetime. 'The Secret Diary of Adrian Mole Aged 13¾' has sold more than 20 million copies

Jeremy Sinclair, ad creative

The pregnant man

the idea appeared to me almost fully formed. It was 1979, at the Cramer Saatchi office on Goodge Street. It was one of my first jobs, I was 23, and the brief was to do a poster that could go up in family planning clinics, which would encourage men to be a little more considerate. The image of the pregnant man came to me a nano-second ahead of the line, which read: "Would you be more careful if it was you that got pregnant?". It amused me – but I worried that a picture of a pregnant man might be a bit shocking.

I hid the picture at the back of my mind and tried to come up with other visuals. I struggled with a few alternatives, which I showed to Charles [Saatchi]. He said, "I love the line but you need a better picture". After a day or so, I told him the original idea was to have a 'pregnant man'; on hearing the words he cried, "This is it!".

My art director, Bill Atherton, drew up a rough with his Magic Marker on paper, as we did in those days, and it was presented to the Health Education Council who immediately gave it the go-ahead. Bill got hold of a photographer, Alan Brooking, and he shot it just as it appeared, using a fake stomach. It was shot against a neutral background, with the guy looking to the camera very forlornly.

We had no idea what impact it would make. We loved it to pieces, but then we loved everything we did. The joy of seeing something come out of nothing on to a page, that surge of energy, is one of the great thrills of the business. Launched in 1971, Cramer Saatchi's pregnant man campaign remains one of the most iconic adverts of all time

Babyface, songwriter

'End of the Road', by Boyz II Men

when you get it right, the feeling is like a rush of energy – but you don't know until the last minute whether you've got it. These are the hit song rules: you need a great melody, a chorus people want to sing along with, and lyrics which, if not exactly clever, in some way capture people.

I've written 42 number one singles for everyone from Whitney Houston and Mariah Carey to Madonna and Michael Jackson. In each case it's about chemistry, because in reality you can think you have all the elements in place, and you can write a song that follows those hit rules exactly, and which by every right should be a hit, but then it's not. No one can write a smash every single time.

"End of the Road", which stayed at number one in the charts for 13 weeks, was written in a small rented house in Atlanta. My writing partner, LA Reid, and I had been asked to do a song for a movie called Boomerang starring Eddie Murphy. They needed a ballad and wanted a band called Boyz II Men to perform it. I wasn't given a theme or storyline, I just knew the group was from Philadelphia and had that old-town Philly style, and I wanted to write a song in that vein. When I finished I knew it was nice, but I didn't realise how nice until I handed it over to the boys.

On the day, we had eight hours to cut the record; we walked in, introduced ourselves and played the song to the band. We had the basic structure, but within five hours we'd finished the whole song. It felt like something new. But we couldn't know what it would do.

For a smash hit to happen, certain things need to come together in the right way: the right voice, the right feeling, the right look. But it's not an exact science, you can't really call it. In 1992, 'End of the Road' won two Grammy Awards and stayed at number one in the US charts for a record-breaking 13 weeks. A new version appears on the Boyz II Men album, 'Twenty'

Vidal Sassoon, hairdresser

The five-point cut

getting it right became an addiction. Suddenly, maybe in the middle of the night, an idea would come and I would have to rush to the salon with a model and see if I could work it out. Within a couple of years I got to the 'Nancy Kwan' style, and from there every season meant a slight progression, working with asymmetry until we arrived at the five-point 'Grace Coddington' cut.

In 1954, I opened my first salon, on Bond Street. I was very unhappy with hair fashion at that time. Architecture and so many other art forms had moved on – I was inspired by Bauhaus and the Whitney Museum in New York City – yet while there were all these wonderful buildings around us to look at, hairstyling hadn't changed one bit. Ladies were still going to the salon twice a week, having their hair slicked and back-combed; and it was an elitist thing too, for people who could afford to go in twice a week for a set, and maybe a couple of feathers, before going to the Ritz for lunch. I thought, this has to change.

Hair is the only substance in the human form which you can use to create shapes and angles, and it moves so beautifully. It took 10 long years for the [five-point cut] to arrive. I knew it would all be in the shape. It was solid work, often getting home at one o'clock in the morning and working weekends. I wanted to harness that and work with a woman's natural bone structure, and the key to that lay in getting the geometry exactly right. The five-point cut earnt Vidal Sassoon the title 'The man who changed the world with a pair of scissors'