Liposomes are microscopic spherical vesicles composed of internal aqueous compartments surrounded by lipid bilayers with membranes formed by natural or synthetic lipids. Liposomes can be monolayered or multilayered, with diameters ranging from nanometers to micrometers. The formation of liposomes is a spontaneous process that occurs when phospholipids or other amphiphilic molecules with specific properties are hydrated. Phospholipids form shells due to the hydrophobic action of acyl chains in aqueous media. This state is thermodynamically favorable and can be enhanced by hydrogen bonding, van der Waals forces, or other electrostatic interactions.