Peptides and proteins are chains of α-amino acids linked in a defined order, they only differ in length. Both types of molecules are omnipresent in living organisms and essential for their functioning. Peptides consist of 2 amino acids at minimum, whereas proteins are assembled from at least 100 of these building blocks (the division is somewhat arbitrary). If not isolated from natural sources, peptides can be produced by chemical means, e.g., by SPPS, whereas proteins are usually produced by recombinant methods. For an in-depth explanation of peptides, take a read of our online peptide guide for beginners.