Nobel Prize-winning chemist Frances Arnold left home at 15 and went to school ‘only when she felt like it’. She disagreed with her parents about the Vietnam War and drove big yellow taxis in Pittsburgh to pay the rent. Decades later, after several changes of direction (from aerospace engineer to biotech pioneer), she invented a radical new approach to engineering enzymes. Rather than try to design industrial enzymes from scratch (which she considered to be an impossible task), Frances decided to let Nature do the work. ‘I breed enzymes like other people breed cats and dogs’ she says. While some colleagues accused her of intellectual laziness, industry jumped on her ideas and used them in the manufacture of everything from laundry detergents to pharmaceuticals. She talks to Jim Al-Khalili about her journey from taxi driver to Nobel Prize, personal tragedy in midlife and why advising the White House is much harder than doing scientific research. Producer: Anna Buckley