Calcium transport into and out of mitochondria — the powerhouses of cells — is central to cellular energy production and cell death. To maintain the balance of calcium within these powerhouses, cells rely on a protein known as the mitochondrial sodium-calcium exchanger, or NCLX. Now, in new research, scientists have discovered a novel regulator of NCLX activity, a protein called TMEM65, which helps move calcium out of mitochondria, protecting against harmful calcium overload.