Photos: Gravity experiments in space
Source:
NASA
Japanese Medaka fish (an embryo is shown here) were among the first animals used to study embryo development in space
The importance of gravity at the start of an animal's life cycle is still a big mystery.
While Medaka fish born in space grew to resemble their Earth-born brethren, experiments on other animals, from mice to clawed toads, have shown that weightlessness can have a significant impact on early development, making many more prone to physical abnormalities.
The International Space Station may still be under construction, but microgravity research has been under way for decades. Here is a round-up of some of the most notable experiments.