At first blush, the brain’s extracellular matrix (ECM) seems like the opposite of synaptic plasticity. Plasticity is the ability to change; the ECM is stable, to the point that it is often described as a scaffold – something to lend stability. “ECM proteins have some of the longest lifetimes of any protein in the brain,” Anna Molofsky told her audience at the XVII Meeting on Glial Cells in Health and Disease, which is being held in Marseille this week.