Places into perspective the role of quantum dynamics in NMR--addresses characterization of a system of particles with spin (or any other quantum mechanical property), how such a system changes with time, and broader applications to chemistry, physics, and other fields. Also ties together the various manifestations of NMR in solids and liquids--using as a common language the unitary transformation of a system's density operator under the Hamiltonian--revealing the underpinnings of what might be called manipulative NMR: experiments in which the time-dependent Schdinger equation is controlled externally in a non-trivial fashion.