A liposome is a vesicle structure with spherical shape composed of one or several phospholipid bilayers. The image illustrates the composition of a simple liposome composed by a mono lamellar phospholipid bilayer.
Figure 1: Representation of the structure and formation of the phospholipid bilayer in a simple liposome.
The formation and structure of the liposomes is due to the amphiphilic nature (with hydrophilic and hydrophobic regions) of the phospholipids that compose it, whose homologous regions are united in aqueous medium, so it is essentially a mechanical process of phospholipids hydration.
When the encapsulated compound is soluble in water, it is positioned inside the structure while in the case of a hydrophobic compound, would be placed in the liposome membrane