A Soyuz rocket has blasted off from Kazakhstan, launching the latest human mission into orbit to join the International Space Station.
The two Russian cosmonauts and one American astronaut are accompanied by 32 fish.
The fish are going to play the role of guinea pigs to see how they adapt to the lack of gravity.
They will be kept inside a space age fish tank called the Aquatic Habitat.
Also on board is a toy hippopotamus, a gift from the daughter of one of the cosmonauts. It is being used to indicate the point when the rocket reaches the weightlessness of space.
The launch was to have taken place last week but was put back for technical reasons.
The mission is scheduled to last five months. The rocket is due to dock with the ISS and its existing three crew members on Thursday.