Membrane remodeling by class II PI3K-C2α is essential for platelet maturation. Megakaryocytes initiate platelet production by extending and releasing intermediate platelet structures called proplatelets into the bloodstream. Released proplatelets undergo a series of remodeling steps to generate mature platelets. Valet et al show that PI3K-C2α generates a distinct pool of PI3P in resting platelets that may modulate membrane elasticity and remodeling by reorganizing membrane skeletal proteins such as spectrin.