Who is listening in on your phone calls? On a landline, it could be anyone, says privacy activist Christopher Soghoian, because surveillance backdoors are built into the phone system by default, to allow governments to listen in. But then again, so could a foreign intelligence service ... or a criminal. Which is why, says Soghoian, some tech companies are resisting governments' call to build the same backdoors into mobile phones and new messaging systems. Learn how some tech companies are working to keep your calls and messages private.

How does knowledge grow? Sometimes it begins with one insight and grows into many branches. Infographics expert Manuel Lima explores the thousand-year history of mapping data -- from languages to dynasties -- using trees of information. It's a fascinating history of visualizations, and a look into humanity's urge to map what we know.

Swallowing pills to get medication is a quick, painless and often not entirely effective way of treating disease. A potentially better way? Lasers. In this passionate talk, TED Fellow Patience Mthunzi explains her idea to use lasers to deliver drugs directly to cells infected with HIV. It's early days yet, but could a cure be on the horizon?

It’s estimated that 150,000 to 1 million Iraqi civilians died as a result of the US-led invasion in 2003. Artist Matt Kenyon wanted to create a monument for them. But rather than build a large stone pillar, he made his monument small in size and easily replicable. He’s spent five years sneaking it into the halls of power -- including directly into the hands of a US Attorney General who held office during the war, in an exchange caught on tape.