This lecture covers the recent developments in the preparation and chemistry of metallacycles and metallacages via coordination, advantages of using transition-metal complexes for supramolecular assemblies, thermodynamic considerations for self-assembly, molecular squares, rectangles, cages, and nanotubes, as well as the stabilization of unusual molecules inside coordination cages. It also discusses the sequence-selective recognition of peptides, helicates including double-stranded and triple-stranded helicates, circular helicates, and catecholate-based helicates, and self-recognition in helicates.