 ‘Environmental’ decoherence is decoherence that arises through suitable interaction of a system with its environment. The study of environmental decoherence consists to a large extent in the construction and investigation of concrete models of such interactions. We have already mentioned taking an environment of relatively light particles that scatter off a relatively heavy particle. Such a model can be used to study e.g. chiral molecules. Or one can take an atom in interaction with the electromagnetic field, or a harmonic oscillator in a thermal bath of oscillators, and many more. Various features of interest typically arise in such models: some are in common to most models, others are highly model-dependent.