Dr Chris Smith and the Naked Scientist team present the latest science news, analysis and breakthroughs, In this week's episode...what the structure of your retina reveals about your risk of developing a range of different diseases, have we finally cracked how the first biological cells appeared 4 billions years ago? And how pond skater insects survive potentially lethal run-ins with large raindrops. Plus we’re continuing our “Titans of Science” series, this week we interviewing Wales former Chief Scientist and Alzheimer's guru, Julie Williams. Get the podcast from the BBC Sounds app.