Space Shuttle Endeavour's final mission, which began Monday, has received a lot of press due to Rep. Gabrielle Giffords' attendance. But what was the actual purpose of the mission?

Answer: To deploy the $2 billion Alpha Magnetic Spectrometer (AMS, pictured above). The Spectrometer is "the most complex space physics experiment ever built," according to the BBC.

"The seven-tonne machine will sit atop the International Space Station and undertake a comprehensive survey of cosmic rays - the storm of high-energy particles (mostly protons and helium nuclei) that are accelerated in our direction from exploded stars, black holes and who knows what other exotic corners of the cosmos.

"In analysing the nature of these particles, AMS promises remarkable new discoveries about how the Universe is put together."