A big piece of a long-standing puzzle—how cells maintain osmotic pressure via volume-regulated anion channels (VRACs)—appears to have been solved, as researchers reported in Cell today (April 10) having identified a key VRAC protein. Ardem Patapoutian of The Scripps Research Institute in La Jolla, California, and his colleagues found that this protein, which they’ve dubbed “SWELL1,” is a critical component of the osmotic channels that help keep cells from swelling until they explode.