Astronaut David C. Hilmers conducts the Microgravity Vestibular Investigations (MVI) sitting in its rotator chair inside the IML-1 science module. When environmental conditions change so that the body receives new stimuli, the nervous system responds by interpreting the incoming sensory information differently. In space, the free-fall environment of an orbiting spacecraft requires that the body adapts to the virtual absence of gravity. Early in flights, crewmembers may feel disoriented or experience space motion sickness. MVI examined the effects of orbital flight on the human orientation system to obtain a better understanding of the mechanisms of adaptation to weightlessness. By provoking interactions among the vestibular, visual, and proprioceptive systems and then measuring the perceptual and sensorimotor reactions, scientists can study changes that are integral to the adaptive process. The IML-1 mission was the first in a series of Shuttle flights dedicated to fundamental materials and life sciences research with the international partners. The participating space agencies included: NASA, the 14-nation European Space Agency (ESA), the Canadian Space Agency (CSA), the French National Center of Space Studies (CNES), the German Space Agency and the German Aerospace Research Establishment (DAR/DLR), and the National Space Development Agency of Japan (NASDA). Both life and materials sciences benefited from the extended periods of microgravity available inside the Spacelab science module in the cargo bay of the Space Shuttle Orbiter. Managed by the Marshall Space Flight Center, IML-1 was launched on January 22, 1992 aboard the Space Shuttle Orbiter Discovery (STS-42 mission).