Does the human body really replace itself every few years? The answer is yes, but different parts of the body do so at different rates. Learn all about which parts of your body are the speediest, and which take the longest to regenerate, in this classic episode.

Selects: Mangroves: Nature's Best Tree?
44:31

How the Kowloon Walled City Worked
41:27

Short Stuff: In-Flight Entertainment
12:23