Sir John Gurdon FRS, Nobel Laureate 2012, describes his research journey from creating the first animal clones through to exploring how cells become programmed to perform different specialised functions. In this eloquent and fully illustrated lecture to a spellbound audience, John illustrates the key findings over several decades that underpin current research into cell replacement therapies. This inspiring event was the closing lecture of the March 2016 University of Cambridge Science Festival, recorded at the Cambridge Biomedical Campus. In 2016 the Gurdon Institute celebrates 25 years of studying development to understand disease.