Self-assembly is a new frontier of chemistry. By constraining the covalent and noncovalent interactions 19 of molecular building blocks, self-assembly organizes molecules to form ordered structures on 20 different length scales. Highly specific supramolecular architectures have been identified within a 21 variety of biologically relevant systems, such as the complementary base pairing in DNA replication, 22 the folding and assembly of polypeptides, the ligand-receptor recognition and signal transduction, and 23 the micellization of lipids. Inspired by the supramolecular structures in nature, numerous functional 24 supramolecular materials have been designed and fabricated in a bottom-up manner, leading to a wide 25 range of technological applications.