A hormone is a class of regulatory biochemicals that is produced in all multicellular organisms by glands, and transported by the circulatory system to a distant target organ to coordinate its physiology and behavior. Hormones serve as a major form of communication between different organs and tissues.
In the early days of the space race, agency researchers in Russia and at NASA really weren't sure all what would happen to an astronaut in space. They didn't know if a human mind could handle actually seeing Earth or what would happen to the human body when exposed to long periods of weightlessness. Would their blood forget which way to pump? Would their eyeballs shift or their inner ears wig out? They sent up mice and monkeys and dogs, to see what happened, and in 1961, the Russians strapped a man to a rocket headed for orbit. Yuri Gagarin was the first person in space. The ultimate human guinea pig, he survived, becoming an international hero.