The invention concerns nanocapsules, in particular with an average size less than 50 nm, consisting of an essentially lipid core liquid or semiliquid at room temperature, coated with an essentially lipid film solid at room temperature having a thickness of 2 - 10 nm. The invention also concerns a method for preparing same which consists in producing a reverse phase of an aqueous emulsion brought about by several temperature raising and lowering cycles. Said lipid nanocapsules are particularly designed for producing a medicine.