NASA has sent vials of frozen bull and human sperm samples to the International Space Station as part of a study aiming to determine whether mammals can conceive in zero gravity. The frozen supplies for the experiment, dubbed Micro-11, were delivered to the ISS aboard SpaceX’s Dragon capsule. Astronauts will now thaw and chemically active the samples using a unique chemical concoction. The sperm’s movements will be closely monitored and filmed as it swims toward and fuses with an egg. After the initial phase, the samples will be mixed with preservatives and then sent back to Earth, where the experiment can be completed.