To understand how humans adapt to space environments many experiments can be conducted on astronauts while they work aboard the Space Shuttle or the International Space Station (ISS). We also need animal experiments that can apply to human models and help prevent or solve the physical issues we face in space travel. The medaka is a suitable model fish for studying space adaptation because in the second International Microgravity Laboratory mission in 1994 adult fish mated successfully in space during 15 days of flight. In 2012 another space experiment Medaka Osteoclast was performed. Male and female fish (6 weeks old at launching) were maintained in the Aquatic Habitat system for 2 months in the ISS. The RNA-seq analysis of tissues from these fish will revealed tissue-specific responsiveness and common stress responses during space adaptation.