Peptides are short polymers of amino acids linked by peptide bonds. They have the same chemical structure as proteins, but are shorter in length. Major classes of peptides are milk peptides, ribosomal peptides, non-ribosomal peptides, peptones and peptide fragments. Peptides have recently received prominence in molecular biology. Inhibitory peptides are also used in clinical research to examine the effects of peptides on the inhibition of cancer proteins and other diseases.