Victor Ambros, US scientist and Nobel Prize winner in Physiology or Medicine, says he was 'astonished and surprised' to receive the prestigious award. During a press conference in Worcester, Massachusetts, Ambros reflects on his immigrant roots and the revolutionary discovery of microRNAs that transformed understanding of gene regulation. "The deeper we understand living systems, the better equipped we are to figure out what's wrong when these systems go awry," he says. IMAGES AND SOUNDBITES