Can be used by cells to store energy, form biological membranes, and serve as chemical messengers.

Lipids

Lipid molecules are incorporated in the plasma membrane as part of the phospholipid bilayer, which has a polar and non-polar end. Lipid molecules are also stored in cells and are more commonly known as fat then. Fat serves as an energy store and insulates organisms from the cold. Glycolipids are molecules found on the surface of cells and help in communication. 

Yes he thought they should be left to chance why, because he thought that was the best thing to do