Small molecules are low molecular weight compounds, typically less than 900 daltons, that can easily enter cells and interact with biological systems. They play crucial roles in various processes, including metabolism, signaling, and regulation of cellular functions. Many small molecules are used as drugs to treat diseases by targeting specific proteins or pathways in the body. In addition to their therapeutic uses, small molecules are also important in research and development. They can serve as tools to study biological mechanisms or as starting points for the design of new medications. Examples of small molecules include aspirin, glucose, and caffeine.