Experiments conducted in space in order to take advantage of the reduced gravity in studies of the growth, behavior, and properties of materials. Spacelab, developed by the European Space Agency (ESA), is a laboratory module that flies in the space shuttle payload bay. First launched in 1983 on the Columbia, the module has become the workhorse for United States and international science missions emphasizing low gravity. Twelve such missions have been flown to date (mid-2001), and an additional seven missions utilized Spacelab components (such as a pallet to support experiments not requiring direct crew interaction). The experiments in fluids, combustion, materials science, and biotechnology conducted on these missions, together with their related ground-based research, have resulted in more than 2200 scientific publications, about 1200 of which appear in peer-reviewed journals.