Cells actively control membrane curvature using a variety of mechanisms. Although membrane lipid (A, B) and protein (C–F) composition can each contribute to curvature generation, the bulk of the energy required for shaping high curvature membranes is provided by specialized curvature-generating proteins. Mechanisms that contribute to membrane curvature generation include, A) phospholipid headgroup composition, B) phospholipid acyl chain composition, C) protein scaffolding, D) amphipathic helix insertion, E) hydrophobic loop insertion, F) conically-shaped transmembrane proteins.