Exocytosis may result in two types of fusion – complete fusion and kiss-and-run fusion.
Complete fusion – In this process, the vesicle membrane and the cell membrane fuse together completely creating a fusion pore, wherein the vesicle becomes part of the cell membrane. The fusion pore enables the vesicle to release its contents to the exterior of the cell.
Kiss-and-run fusion – In this process, the vesicle and the cell membrane fuse temporarily. The fusion only lasts long enough to create a fusion pore from where the vesicle can expel its contents outside the cell. Once the contents are expelled, the vesicle detaches from the cell membrane and returns to the interior of the cell.