We review efforts to construct a self-consistent model of pulsar magnetospheres that links the particle source near the pulsar to the outflowing relativistic wind and couples the wind to the surrounding nebula. Pair production source models (Sturrock, 1971; Ruderman and Sutherland, 1975; Arons, 1979) produce outflowing positronic plasmas which are too dense to support a plasma wave of relativistic amplitude (Kennel et al., 1973). Therefore an appropriate description seems to be a relativistic magnetohydrodynamic (MHD) wind. Radiation from a relativistic wind will be collimated forward and can only be observed along the line of sight to the wind source. This makes relativistic winds essentially unobservable and provides an almost invisible method of energy transport. Photons can be emitted in all directions and the existence of the wind inferred only after the wind has been decelerated by a confining shock (causing the flow to become subsonic and non-relativistic).