PubChem is a part of the National Center for Biotechnology Information (NCBI), a division of the U.S. National Library of Medicine.
Since 2004, PubChem mostly contains small molecules, but also larger molecules such as nucleotides, carbohydrates, lipids, peptides, and chemically-modified macromolecules. We collect information on chemical structures, identifiers, chemical and physical properties, biological activities, patents, health, safety, toxicity data, and many others. The data in PubChem comes from e.g.: government agencies, chemical vendors, journal publishers, and more.