Cell Biology The tension of a cell's plasma membrane influences many processes that require membrane remodeling, including cell migration and endocytosis. However, little is known about how organelle membrane tension may regulate cell function. After endocytosis, endosomal membranes are remodeled in an ESCRT-III–dependent process that leads to the formation of intralumenal vesicles (ILVs). Mercier et al. investigated this phenomenon using a specific fluorescent membrane tension probe. ESCRT-III subunits were recruited to endosomal membranes as membrane tension reduced. Tension-dependent membrane recruitment was associated with ESCRT-III polymerization and membrane deformation and with increased ILV formation. In cultured cells, endosomal membrane tension decreased when ILV formation was triggered by epidermal growth factor. Thus, endosomal membrane tension regulates ILV formation, and reduced tension facilitates intracellular membrane-remodeling processes. Nat. Cell Biol. 22 , 947 (2020).