Veteran British scientist John Gurdon, who shared the Nobel Prize for medicine on Monday, is often described as the 'godfather of cloning' for his work on stem cell research.
However, he was once told by his teacher not to pursue a career in science.
Based at Cambridge University, Gurdon shared the prize with Shinya Yamanaka of Japan for work on reprogramming cells, which offers hope to people whose lives are blighted by disease.
Gurdon, born in 1933, rose to prominence in 1962 when he took the genetic code from a cell in a frog's intestines and transplanted it inside a frog egg, which developed into a normal tadpole.
The pioneering research helped clear the way for further work on cell programming.
Gurdon is fond of recalling that when he was 15, a tutor wrote in his school report that it would be a 'total waste of time' if he followed a career in biology 'and this whole idea should be immediately discouraged'.
He has said he keeps the report above his desk 'for my amusement'.
His mother though had spotted that he was fascinated by the subject.
'Even at school I used to grow thousands of caterpillars to make moths, to the intense annoyance of my tutor,' Gurdon said in an interview several years ago.
'But I had a fascination for these things, and I think it was really she particularly who enabled me to switch from my education, which was completely non-scientific, into a scientific direction.'
When it came to choose a career, his father wanted him to go into the army or banking.
'Fortunately for me, I was refused entry to the army for the national service, a piece of good luck,' he recalled.
'I was actually a competitive squash player at the time and rather fit, but the family doctor decided I was not suitable for the army and diagnosed my slight cold as bronchitis, and that eliminated any possibility, thank heavens, of entering the army as a career,' he said.
He managed to win a place at Oxford University. His first intention had been to study classics, but the admissions tutor said he would grant him a place providing it was not in that subject.
His post-doctorate thesis was on nuclear transplantation, the subject that has obsessed him throughout his career.
In 1971, he moved to Oxford's great rival, Cambridge, and in 1989 Gurdon started the prestigious Wellcome/CRC institute at the university.