Nobel Prize-winning Briton Professor Sir John Gurdon has told ITV News his teacher dissuaded him from studying science at school.
Sir John admitted he was "bottom of the bottom form" in his year at Eton and his teacher thought his studying science was "a completely ridiculous idea".
But Sir John proved that teacher wrong when he was awarded the Nobel Prize for Medicine alongside leading Japanese stem cell scientist Professor Shinya Yamanaka.
In 1962, Sir John successfully cloned the South African frog Xenopus from a tadpole's intestinal cell while still a graduate student.
Sir John produced a genetically identical tadpole by transplanting the cell nucleus into an empty Xenopus egg cell.
This pivotal discovery paved the way for future cloning research.
Sir John told ITV News receiving the Nobel Prize for Medicine was "amazing".
He said, "You imagine it's all a dream and you'll wake up the next day and find it was indeed a dream and you're back to work as usual. So that's the first reaction you have - and then gradually you hope that it's actually true".
Sir John was born in 1933 in Dippenhall, Surrey.
He received his Doctorate from the University of Oxford in 1960.
He was a postdoctoral fellow at California Institute of Technology.
He joined Cambridge University in 1972
Sir John served as Professor of Cell Biology and Master of Magdalene College.
He is currently at the Gurdon Institute in Cambridge.
In 2006 Professor Yamanaka, from Kyoto University, showed how mature cells in mice could be made to revert to a youthful embryonic state.
Like stem cells from embryos, the "induced pluripotent stem cells", or iPSCs, had the potential to develop into any kind of cell in the body.
The Nobel Prize recognizes two scientists who discovered that mature, specialised cells can be reprogrammed to become immature cells capable of developing into all tissues of the body. Their findings have revolutionised our understanding of how cells and organisms develop. These groundbreaking discoveries have completely changed our view of the development and cellular specialisation. We now understand that the mature cell does not have to be confined forever to its specialised state. Textbooks have been rewritten and new research fields have been established. By reprogramming human cells, scientists have created new opportunities to study diseases and develop methods for diagnosis and therapy.
Both scientists will share the prize money of eight million Swedish kronor (£750,000).
University of Edinburgh Professor Sir Ian Wilmut, who led the team that cloned Dolly the Sheep, congratulated the Nobel Prize-winning pair saying, "I am delighted that the committee has recognised their important and innovative work on cellular reprogramming and its importance for regenerative medicine".