Substituted tryptamines, or simply tryptamines, also conceptualizable as serotonin analogues, are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all tryptamines contain an indole ring, joined to an amino (NH₂) group via an ethyl (-CH2–CH2-) sidechain. In substituted tryptamines, the indole ring, sidechain, and/or amino group are modified by substituting another group for one of the hydrogen (H) atoms.