The Astrobees are free-flying robots that operate inside the International Space Station (ISS) and were launched to the ISS in 2019. Since then they have successfully performed hundreds of activities in space supporting almost two dozen separate research projects. The robots were designed to overcome multiple challenges unique to the ISS environment, including safety, upgradeability and maintainability, limited mass and computation, and unique localization challenges from lack of gravity and a constantly changing environment. This article provides an overview of Astrobee, from hardware and software design to deployment results and activities.