When unfolding a tent for the first time, you may wonder how the huge tarpaulin fits into a bag the size of a football. Biologists wonder about something similar: when a cell divides, the surface area of the cell membrane grows. Moreover, when molecules are brought from one organelle to another inside the cell, membrane-enclosed transport vesicles are formed. So that membranes can be made available quickly, they are stored within the cells in the form of nanotubes, tubular membrane structures - similarly to a tarpaulin that has been folded together.