Learn the basics of how black holes form, their different sizes, and how they were found.

Top secret : for your eyes only! -- Black holes : the basics -- Types of black holes -- Fact file : discovering black holes -- How to see a black hole -- Blazars and quasars -- Danger on the event horizon -- Spaghettification -- An impossible picture -- Wormholes -- Black hole crash -- Fact file : Cygnus X-1 -- Penrose energy.