Large endocytic vesicles are retrieved rapidly through ultrafast endocytosis, but their fate is unknown. Watanabe et al. used the 'flash and freeze' technique to show that at physiological temperatures, stimulation of mouse hippocampal neurons results in clathrin-independent formation of large endocytic vesicles, which transition to the endosome and later bud off in a clathrin-dependent manner to form small synaptic vesicles. Notably, when the same experiment was performed at room temperature, synaptic vesicles were endocytosed by classic clathrin-mediated endocytosis. This might explain some of the apparently conflicting results in the field.