A robotic cell culture bioreactor system was developed and tested on space shuttle flight STS-95 in 1998. The system contains a single 50-mL bioreactor with options for rotation (or not) at a few RPM, perfiision, oxygenation and timed sampling. This reactor system is suitable for cells (animal, plant, microbial) and tissues of all types and aquatic organisms. It can also serve as a large-scale crystallization reactor or emulsion polymerization reactor. Fresh medium is fed by peristaltic pump to the reactor at a rate specified by the experimenter. Up to six samples of the supernatant or unfiltered culture can be collected at specified times during flight. Each bag into which samples are collected can contain a fixing solution or RNAextraction reagents. Each robotic system fits into a standard sealed cassette housing for operation in a single-locker processing facility, which was flightproven on shuttle missions STS-77 and STS-95 and capable of operating three cassette-based experiments simultaneously. The processing of experiments in cassettes is totally automated. The only crew tasks are the removing and inserting of cassettes. The three independently controlled processing modules can be controlled via telemetry. A separate locker with temperature-controlled storage is typically used for stowing sample cassettes while they are not being processed.