Your blood is always red. So why the bruise rainbow? This episode explores the colourful chemistry of bruises, from love bites and cupping to creatures with blue, green and yellow blood - and what Tiffany & Co.'s famous turquoise packaging has to do with it.

This episode explores the history hidden inside your belly button, from Renaissance arguments over whether Adam had a navel, to the doctor who classified sixty different types of belly button, to the German students who deliberately collected facial scars to improve their marriage prospects.

Classify your own belly button using Thomas Cullen's 1916 guide.

The marathon wasn't designed by sports scientists. It was shaped by an ancient legend, a royal whim, and one spectacularly bad Olympic experiment involving purposeful dehydration, brandy, and rat poison.

A famous biology textbook diagram. A Harvard psychologist called Edwin Boring. And somehow... netball. This episode explores the mad history of the tongue map, and why taste exists in the first place.

If you thought doing sit-ups would give you a six-pack, think again. This episode explores the gruelling reality of competitive bodybuilding, and how a 19th century circus strongman used a tape measure, Greek statues, and a little mathematics to define the ‘perfect’ physique. (Do you measure up?)

In one experiment, a man who didn't sleep for a week ended up sobbing about an imaginary gorilla. This episode explores what science has uncovered about the effects of sleep deprivation, from hallucinations to frank psychosis – and whether the brain recovers afterwards.

The inventor of Corn Flakes believed cinnamon was morally suspicious and flavour was a threat to virtue. This episode explores the strange story of John Harvey Kellogg, his wellness empire, his obsession with chewing, vibrating chairs for constipation, and why evolution made flavour far too appealing for his crusade to succeed.

In 1980, flight attendants began apparently sweating blood on flights between New York and Florida. The CDC investigated. The explanation was not what anyone expected. Also featuring blue sweat, pink sweat, and the only diagnostic dilemma ever solved by a dermatologist ringing a snack-food manufacturer.