On board the International Space Station (ISS), astronauts take part in long-term missions performing experiments onboard and operating the station’s systems. They assemble, activate and test station components, carry out scientific experiments and even act as test subjects for life science trials. To prepare for their mission, astronauts complete a three-phase training program. During their one-year basic training they get familiar with the space agencies and their programs. Basic knowledge of space and electrical engineering as well as several scientific disciplines are covered as well and at the end of the basic training, they complete a diving course as a basis for extravehicular activities. Under water, the astronauts in their space suits can float – almost – as they do in space. The buoyancy of their bodies when diving is similar to weightlessness. Last but not least they receive Russian language classes, behavioral and performance skills training. The second phase is a one-year advanced training, focused on skills required on any ISS mission: operation and maintenance of ISS modules, systems, payloads and transporters, handling of resources and data, robotics, navigation, maintenance, onboard and extravehicular operations, knowledge of payloads, medical understanding and even a paramedic training for two crew members per flight. The final training phase is called increment-specific training. It provides the crews with the complete knowledge and skills required for their mission. This approximately 18-month phase also strengthens the bonds and team spirit of the crews.