The term nanotechnology has come to be defined as those systems or processes that provide goods or services that are obtained from matter at the nanometer level, that is, from sizes in the range of one-billionth of a meter. The new technology thus allows the engineering of matter by systems or processes that deal with atoms where the laws of chemistry and physics work differently than at the macroscale because the powers of hydrogen bonding, quantum energy, and van der Waals’ forces endow some nanomaterials with unusual properties. This chapter summarizes a wide range of nanotechnology process topics by addressing the early history of the technology, fundamental and basic principles, nanomaterials, current implementation in environmental technology, and environmental concerns. An application section provides four Illustrative Examples related to the general subject of nanotechnology and its environmental applications.