Radio emission from this remnant of the supernova of 1572 is produced by extremely energetic electrons gyrating in a magnetic field. The morphology of the spherically expanding blast wave from the supernova explosion is clearly visible. The observed strength of emission suggests that electrons are accelerated, and magnetic field amplified, at the shock wave. These observations, in connection with earlier theoretical work, may help elucidate the concrete physical mechanisms by which the inferred acceleration and field amplification may be occurring. As well, the quantitative profile of radio emission from the outside of the remnant, through the bright rim and down to the central plateau, can yield information on the density structure and dynamics of the expanding gas.