In recent years the concept of "colloidal devices" has emerged. These include colloidal crystals with photonics properties, as well as displays, machines, and other assemblies having a particular purpose. The assembly of colloidal devices, or even simpler assemblies, can proceed with top-down approaches, applied fields, bottom-up approaches, or combinations of these. Bottom-up assembly, in which the particles have "colloidal force information" encoded chemically on their surfaces and interiors, appears to be especially suited for larger-scale production. The encoded information directs how the particles assemble and function, and a simple example is a colloidal crystal that has purely repulsive forces between all the particles. A richer assembly process can occur with site-specific chemistry, which sometimes occurs naturally on particles, such as when a particle has two different crystal faces. And in recent years, researchers have developed techniques for intentionally placing site-specific chemistry on particles, enabling assembly to proceed through localized electrostatic, van der Waals, depletion, hydrophobic, and receptor-ligand forces. Site-specific colloidal forces are useful in effecting colloidal and nanocolloidal assembly for state-of-the-art and future structures and devices.