What use to science is a pesky organism that feeds on rotting fruit? Professor Bambos Kyriacou has spent fifty years observing the behaviour of fruit flies. He keeps them in the lab and in his garden in their thousands, has recorded fruit fly courtship songs using a microphone loved by Jonny Carson (because it made his voice sound deeper) and invented equipment to keep track of their sleeping patterns. He tells Jim Al-Khalili how fruit flies sparked his interest in genetics and how experiments with insomniac fruit flies opened our eyes to the fundamental importance of body clocks.

Leon Barron monitors pollution in our rivers, keeping tabs on chemicals that could be harmful to the environment and to our health. He’s also gathered intelligence on the behaviour of millions of Londoners by studying the water we flush down the loo. His analysis of sewage revealed, for example, just how much cocaine is consumed in London every day. And he’s helped the Metropolitan Police to crack crimes in other ways too, inventing new chemistry tools that can be used by forensic scientists to uncover clues. At school he had no idea he wanted to be an analytical chemist but a short work experience placement at the fertiliser factory convinced him that this kind of detective work was fun. Producer: Anna Buckley

Tim Lamont is a young scientist making waves. Arriving on the Great Barrier Reef after a mass bleaching event, Tim saw his research plans disappear and was personally devastated by the destruction. But from that event he discovered a novel way to restore coral reefs. Playing the sounds of a healthy coral reef entices fish in to recolonise the wrecked reefs. Tim's emotional journey forced him to realise that environmental scientists can no longer just observe. They need to find new prisms with which to view the world and to intervene to save or protect the natural environment.

Daphne Koller was a precociously clever child. She completed her first degree – a double major in mathematics and computer science – when she was just 17 and went on to become a distinguished Professor at Stanford University in California. But before long she’d given up this comfortable academic position to create the biggest online education platform in the world. In 2018, she founded the drug discovery company Insitro hoping to create a space where data scientists and molecular biologists could work together as equals. Daphne tells Jim Al-Khalili how a single question from her supervisor nudged her to use her considerable mathematical ability to do something useful and why she believes the time is right for artificial intelligence to discover new medicines. Producer: Anna Buckley

Emily Holmes is a distinguished Professor of Clinical Psychology at Uppsala University and a neuroscientist who struggled to learn to read and write as a child. She tells Jim Al-Khalili about her work as a mental health scientist and her life-long love of art and explains why the images we see in our mind’s eye have more of an impact on our emotions than their verbal counterpart. And describes how this fundamental insight led her to develop a simple and cost-effective treatment for the fleeting flashbacks that haunt people with post traumatic stress disorder: briefly recalling the traumatic event and playing the computer game Tetris. Producer: Anna Buckley