Transmission electron micrograph (TEM) of lipid droplets (yellow) in a testicular interstitial cell. They exhibit little or no osmiophilia. It is likely that the differences in osmiophilia of the lipids are reflections of the differences in the degrees of saturation of their constituent fatty acids. The cisternae (orange) of the smooth endoplasmic reticulum are in close apposition to the lipid, creating the erroneous impression that the droplets themselves have a limiting membrane. THE CELL 2nd Edition.