What's inside a space suit? Other than a heroic space adventurer?
Now, thanks to a set of amazing X-ray images created by the Smithsonian Institute's Air and Space Museum.
A new exhibition ('Suited For Space') opens at the museum on Friday, designed to give visitors to the already-extraordinary building an even better look inside the suits that allowed humans to explore the moon.
The Images include X-rays of the 1964 A4-H "Universal" helmet, above, showing off the ball bearings in the neck ring that allowed the helmet to rotate without restrictions.
Other images include overshoes worn by Apollo astronauts when walking on the moon, and a complete experimental space suit made by the Air Research Corporation in 1968.
Cathleen Lewis, a historian and curator of International Space Programs at the museum, told National Geographic that the strange coils inside the suits were to help astronauts move their joints inside the pressurised micro-atmosphere of the suit.
"The shoulder area allows astronauts to localize air displacement and restrain the pressurization," she said. "The joints were designed to automatically localize the displacement of air."
Here are some other amazing pictures of the space suits, which will be on show in Washington DC until 1 December.