Mechanosensitive channels are membrane proteins that open and close in response to mechanical forces produced by sound, gravity, osmotic pressure, or other mechanical stimuli. In the open state, these proteins allow passage of ions across the cell membrane, thus generating an ionic current that eventually becomes an electrical signal (mechanotransduction) or that regulates cell volume. In a new paper in Science (August 29), researchers in Klaus Schulten’s group, in collaboration with alumnus Marcos Sotomayor (now at Harvard) and scientists at the University of Chicago, report the structural changes of a key membrane protein (MscS) in response to osmotic challenges.