Peptide-based semiconductors For semiconductors, one often thinks of inorganic materials, such as doped silicon, or aromatic organic polymers and small molecules. Tao et al. review progress in making semiconductors based on self-assembling short peptides. The structures that form show extensive π and hydrogen bonding leading to a range of semiconductor properties, which can be tuned through doping or functionalization of the peptide sequences. These materials may shed light on biological semiconductors or provide an alternative for constructing biocompatible and therapeutic materials. Science , this issue p. aam9756