Physicist Max Tegmark uses a waterfall analogy to explain how black holes work, how the event horizon is the point of no return, and what it would be like to go through one.
Physicist Douglas Leonard explains the relationship between black holes and the sun, and reveals how the Hubble Telescope helped discover a black hole where sun had gone supernova.
A quick exploration of the huge variety of plants in the world, from a pine tree that is thousands of years old, to a bamboo that grows 30 metres high in just 90 days.
David Attenborough introduced us to some amazing flowering plants and the complex relationship they have with pollinators.
Plants need the right balance of nutrients to survive - and some have become carnivorous to ensure they get what they need.
This is a test clip
Michael Moore meets National Rifle Association president Charlton Heston to discuss America's gun culture and the shooting death of a sixyearold girl by one of her classmates.
National Rifle Association president Charlton Heston speaks at the organisation's convention in Denver, near Columbine, shortly after the massacre and is met my protesters.
Michael Moore leads two injured victims of the Columbine shooting and a media pack to KMart's headquarters to deliver bags of 9mm bullets purchased at the store. A spokesperson announces the withdrawal of such ammunition from sale.
Musician Marilyn Manson is amongst those blamed for the Columbine massacre after it is revealed that the shooters were fans. (Coarse language).
Michael Moore compares gun violence statistics and cultural differences around the world. An animation of American history, guns and the Second Amendment is included. (Depictions of violence).
Duncan Watts reveals how the game and urban myth of Six Degrees of Kevin Bacon helped shape his Small World Project and network theory.
Russians recount NKVD implementing Stalin's murderous campaign of political repression.
Helen Hyunh explains how the children of Vietnamese children were raised to value education highly and had a role in translating English for their parents.
Teenagers love to sleep in and it's nothing to do with being lazy. Biology dictates that their body clocks work differently than those of children and adults.
Michael Mosley gets an MRI scan to see how much internal fat he has. It's not good news.
Scans of brain activity reveal decisions can be predicted even before a subject is conscious of them.