Before they were born, these mice were astronauts. Or, rather, the sperm that would go on to deliver half of their genetic material were.
For nine months, mouse sperm was kept aboard the International Space Station, freeze-dried to preserve it. Brought back to Earth, the sperm was rehydrated, introduced to an egg and allowed to divide for about 20 days. The resulting mouse pups carry the distinction of having traveled perhaps the farthest distance ever on their way to being born.
Sperm In Space