It depends on why you mean by "fat" molecules. Lipids in general are usually composed of carbon, hydrogen, and oxygen but they can contain other elements such as phosphorous or nitrogen.

Fat molecules

Fatty acid molecules and glycerol molecules.

Lymphatic vessels serve to absorb fat molecules from the small intestines.

saturated fat molecules are much stronger than unsaturated fat molecules due to the "saturation" of hydrogen atoms attached to the carbon molecules. such molecules are therefore inherently stable and require and enormous amount of energy to release the hydrogen molecules from the sequestered carbon.