This is the one that youll quite often see at the movies, and there appears to be some controversy as to what actually happens when the human body is exposed to the vacuum of space. Lets get a couple of things straight: Firstly you wont freeze to death yes I know, space is pretty chilly, in fact its almost as cold as cold can be; but in order for heat from your body to be transferred, there needs to be something for your body to transfer it to, and since theres effectively nothing in space you wont get cold very fast. Secondly you will not explode, yeah your body exerts internal pressure to counteract the effects of pressure we feel here on Earth, but its simply not enough to overcome the chemical bonds that hold the skin together. Thirdly for the same reason as stated previously, your blood wont boil, because the skin is strong enough to hold everything together in a vacuum your body and everything inside of it is protected from the vacuum in a so called closed system, where the pressure is similar to that found on Earth. What would happen though, is that all of the air in your lungs and the gas in your digestive tract (which are not a part of this closed system) would forcibly push its way out of the nearest orifice. This forceful expulsion of gases would mean that first of all, youll literally crap yourself, and then pretty shortly afterwards suffocate to death. If however, you managed to remain conscious for more than 10 seconds or so youd be witness to a very strange phenomenon as a result of there being no pressure in space, the boiling point of water is reduced to 0 Kelvin (more or less). This means that the saliva in your mouth, the tears in your eyes and even the moisture inside of your now empty lungs would begin to boil and evaporate into the void. Further gruesome transitions do occur to the body after this point, but perhaps some things are best left undiscussed