Liposome Structure
Phospholipids in liposome are amphipathic, that is, part of their structure is water-soluble (hydrophilic or water-loving) and the other part is oil-like which made of a long hydrocarbon chain (hydrophobic or water-fearing or fat-soluble). Therefore, when added to water, the water-soluble part of the phospholipid interacts with the water and the oil-like part of the molecule avoids the water.
In a cell, one layer of heads faces outside of the cell, attracted to the water in the environment. Another layer of heads faces inside the cell, attracted by the water inside the cell. The hydrocarbon tails of one layer face the hydrocarbon tails of the other layer, and the combined structure forms a bilayer.

The interior of liposomes is filled with water and therefore, molecules which are soluble in water can be encapsulated in the interior of the liposome. A less recognized but very important property of liposomes is that molecules which are not water soluble, or oil-like, can be entrapped in the oil-like portion of the phospholipid bilayer. Consequently, liposomes can serve as carriers for all types of molecules including both water-soluble and water-insoluble compounds. In fact, a single liposome can carry both types of molecules or combinations of each type of molecule.
Liposome Phospolipids

Liposomes usually contain a core of aqueous solution; lipid spheres that contain no aqueous material are called micelles, however, reverse micelles can be made to encompass an aqueous environment. Liposomes should not be confused with micelles and reverse micelles composed of monolayers. When membrane phospholipids are disrupted, they can reassemble themselves into tiny spheres, smaller than a normal cell, either as bilayers or monolayers. The bilayer structures are liposomes. The monolayer structures are called micelles. Read More : Liposomes and Micelles Differences and Similarities