The term "small molecule" refers to a type of chemical compound that is relatively simple in structure, typically consisting of fewer than 100 atoms. These molecules are usually less complex than larger or more complicated molecular structures such as proteins, nucleic acids, and carbohydrates. Small molecules can include various substances like vitamins, hormones, drugs, and other organic compounds that have a low molecular weight. They play an important role in many biological processes and are the target of numerous pharmaceuticals.