1. Carbohydrates: These are the primary source of energy for living organisms. They are composed of carbon, hydrogen, and oxygen. Examples include sugars, starches, and cellulose.

2. Lipids: These are fats, oils, and waxes. They are composed of carbon, hydrogen, and oxygen, but with a higher proportion of carbon and hydrogen than carbohydrates. Lipids provide insulation, store energy, and form cell membranes.

3. Proteins: These are complex molecules composed of amino acids. They are involved in almost every biological process, including catalyzing reactions, transporting molecules, and providing structural support.

4. Nucleic Acids: These are complex molecules that store and transmit genetic information. They are composed of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base. The two main types of nucleic acids are DNA and RNA.