The Russian dogs, Belka and Strelka, were the first dogs to spend time in space and come back safely.
They were sent into orbit in August 1960 on board the Russian spaceship, Sputnik 5. After a full day in space, the dogs landed back on earth.
With them on their day-long trip to outer space were 42 mice, 1 rabbit and 2 rats. All the animals came back alive, but only the dogs became famous Russian stars.
Strelka later gave birth to six puppies. One of the puppies was given as a gift to Caroline Kennedy, the daughter of US President John F. Kennedy. Caroline named the dog Fluffy.
After Belka and Strelka died, their bodies were stuffed and put on display in a Moscow Space Museum. Their pictures were used on postage stamps, and their story became the very popular Russian cartoon, Belka and Strelka - Star Dogs.