The plasmasphere is a high‐density, toruslike inner magnetospheric region whose configuration and dynamics are highly sensitive to disturbance activity in the solar‐terrestrial environment. Although many space scientists consider the plasmasphere to be a phenomenon of modest geophysical importance, one that has long been relatively well measured and understood, I disagree. The dynamic plasmasphere remains a theater of discovery as well as an arena for problem solving. It is geophysically important and offers many exciting and largely unmet challenges to both the experimenter and the theorist.