* Carbon (C): This is the backbone of all organic molecules. Carbon's ability to form four bonds with other atoms allows for the creation of a wide variety of complex structures.

* Hydrogen (H): Hydrogen is often bonded to carbon, forming hydrocarbons.

* Oxygen (O): Oxygen is found in many functional groups, such as alcohols, ketones, and carboxylic acids. It is also present in carbohydrates, lipids, and proteins.

* Nitrogen (N): Nitrogen is found in proteins, nucleic acids, and many other biologically important molecules. It is also found in certain functional groups like amines and amides.

Other common elements:

* Sulfur (S): Found in some amino acids, proteins, and certain vitamins.

* Phosphorus (P): Found in nucleic acids, phospholipids, and ATP.

* Halogens (F, Cl, Br, I): Found in some synthetic organic compounds.

* Metals (Na, K, Mg, Ca): Found in some organic compounds, often as part of salts.

It's important to note that while these elements are most common, organic compounds can also contain other elements in trace amounts. The specific composition of an organic compound determines its structure, properties, and function.