In the second episode, Dreadnoughtus males compete for the right to mate. Lizards are hunted by Velociraptor among a group of sleeping Tarbosaurus. A Mononykus forages for termites and investigates new food options after a brief rainstorm. Several types of dinosaurs congregate around a watering hole in Mongolia.
Above the deserts of North Africa, aerial combat ensues as male Barbaridactylus pterosaurs fight for the attention of females below. A herd of Secernosaurus brave the harsh gypsum dunes in search of nourishment.

A third of the population regularly struggle with our sleep, which rose to one in two during the pandemic - the highest it's ever been. However, as more and more people seek help, an explosion in sleep science is enabling the study of sleep in ways not possible before. What's more, recent breakthroughs are uncovering what's happening in our brains and bodies while we're asleep, getting us closer than ever to understanding the importance of sleep for our health. Michael Mosley shows why cutting our sleep short can be linked to a host of illnesses, including serious diseases like Alzheimer's.
Revealing the very latest science breakthroughs and packed with personal anecdotes, this programme is a useful guide to anyone looking for tips and insights on how to get the benefits from learning how to sleep well.

Each night, across the planet, our cities illuminate the darkness. Their lights burning brighter than ever before. And whilst we're asleep, animals are making the most of this new neon landscape. The sunset in Los Angeles, Chicago, and Toronto creates worlds of opportunities for the cleverest animals willing to take the risk.

The second episode of the series looks at dreams and tries to explain what happens in the brain and body after we go to sleep. It looks at the significance of dreams and what dreams can teach us about ourselves. It talks to neuroscientists who discuss slow-wave sleep and REM (rapid eye movement) sleep during which dreams occur. It looks at the history of dream interpretation and its validity.

Why do we sleep? And what does sleep have to do with memory, trauma, and our emotions? From fruit flies to whales, virtually every animal sleeps. But why? Why do we need to spend nearly a third of our lives in such a defenseless state? Scientists are peering more deeply into the sleeping brain than ever before, discovering just how powerful sleep can be, playing a role in everything from memory retention and emotional regulation to removing waste from our brains. So why are we getting so little of it?

Gaby Roslin and Amir Khan present a program in which they apply the latest science to some of the worst sleepers. They include an extreme snorer, a man who suffers from night terrors, a woman who has restless leg syndrome, and a man with chronic insomnia for 20 years.
The film also shows a sleep deprivation experiment to test for risky behaviour, pain resistance and emotional control. When the subjects reach the final hours of the challenge, the experiment begins to take its toll as the participants' emotions go into overdrive, with one threatening to quit altogether.