Many of us take dietary rules for granted such as eating little and often, not skipping meals and keeping a check on our calorie intake. But genetic epidemiologist Professor Tim Spector argues we need to re-evaluate what we think we know about a good diet: diversity in both the types of food we eat and in the unique mix of microbes we nurture in our gut is the most important factor for health. In a multi disciplinary career following early training as a rheumatologist, Tim founded the UK Twins Registry at Kings College London to unravel the extent to which genes contribute to a vast range of human conditions and diseases. But the puzzling differences he observed in identical twins would fuel his current research on the gut microbiome and the discovery that each of us has a unique mix of gut bacteria – in effect a chemical factory that dictates our highly individual responses to different foods. Tim tells Jim Al-Khalili how his research has evolved to successfully develop a new scientific approach to personalised nutrition – through technology that during the pandemic has famously been pressed into service to track Covid symptoms across the UK, and that’s now revealing how a diverse diet has huge implications for Covid-19 outcomes. Producer: Adrian Washbourne

Could the lessons learnt during the pandemic put us in a stronger position to tackle other big science-based challenges ahead, such as achieving carbon net zero, preserving a diversity of species, and protecting our privacy and slowing the spread of misinformation online? As Chief Scientific Adviser to the government during a pandemic, Patrick Vallance's calm, clear summaries of the state of our scientific understanding of the virus were welcomed by many. But what was going on behind the scenes? In this extended interview with Jim Al-Khalili, Patrick opens up about the challenges involved in presenting scientific evidence to government and together they explore that trickiest of relationships - the one between scientists and politicians. He also looks to the future. Scientists gain prominence during a crisis but the need for scientific input to government is ever present. As head of the new Office for Science and Technology Strategy, based in the Cabinet Office, Patrick hopes to put science and technology at the heart of policy making in government. Science should be as central to government as the economy, he says and tells Jim how he thinks that could be achieved. Producer: Anna Buckley

How damaging is the stereotype of white males in white coats? Do scientists think differently? Or do the qualities we associate with being a nerd do them a disservice? Is specialism the best way to solve 21st century problems when so many great discoveries are made in the cracks between the disciplines? In short, what makes a scientist, a scientist? Jim and distinguished guests consider the lessons learnt from nearly 250 leading scientists talking with extraordinary honesty about their life and work. And ask: has the job description changed? Success in science is often defined by making discoveries and publishing papers but, as the pandemic made clear, we also need scientists who can interact with decision makers in government and elsewhere. Do scientists need to learn new skills to participate in the decision making process? Do they (or at least some of them) need to be more outward looking, aware of the world beyond their laboratories and ready to engage? Or do the corridors of power need to open their doors to more people with a scientific training? And, if Britain is to become a science superpower, is it time that scientists stopped being squeamish about making money? Jim's guests are Chief Executive of UK Research and Innovation, Prof Dame Ottoline Leyser; Nobel Prize winning biologist and Director of the Crick Institute, Prof Sir Paul Nurse; geologist and Royal Institution Christmas Lecturer, Prof Christopher Jackson; and forensic scientist and member of the House of Lords, Prof Dame Sue Black. Producer: Anna Buckley

This summer, many parts of the world have seen devastating flooding, from New Orleans and New York, to the UK, Germany and Belgium. More than 300 people lost their lives in floods in central China, including a number who were trapped in a subway train in the city of Zhengzhou. Professor Hannah Cloke of the University of Reading is a natural hazards researcher and hydrologist, who spends her time trying to prevent these terrible losses. She models where flooding is likely to happen and advises governments. Hannah Cloke talks to Jim al-Khalili about how her fascination with the water on the earth goes back to her childhood – her memories of holidays for instance all revolve around swimming or building dams on the beach. She is now passionate about finding new ways of telling the public about the dangers of flooding, which includes writing poetry.

How many of you have sleep problems? Maybe it’s waking up in the middle of the night and then not being able to get back to sleep, or waking up too early, or nodding off all too often in front of the TV… or, more embarrassingly, during work meetings? One thing’s for sure: our modern world means that we are not sleeping in the way we used to. Derk-Jan Dijk, Distinguished Professor of Sleep and Physiology at the University of Surrey and Director of the Surrey Sleep Centre, says: we are the only species to extend our day using artificial light, and that has consequences. Jim Al-Khalili talks to Derk-Jan Dijk about the many aspects of sleep that he has studied over the last thirty years – such as how circadian rhythms interact with our sleep cycles, and how sleep changes in people with dementia.