Calcium, the most important of the second messengers, locally modulates the excitability of nerve and muscle. Calcium enters cells through single-protein channels in the cells' outer membrane. We exploit the ability to dynamically monitor cytosolic calcium, throughout intact cells, with sub-millisecond temporal resolution and sub-micron spatial resolution in the construction of a map of channel density. In the process we pose and solve two inverse problems for the associated semilinear system of reaction diffusion equations:

(1) Infer from the change in cytosolic calcium Fluorescence the associated membrane calcium current in space and time, and

(2) Infer from the calcium current the nonuniform distribution of calcium channels.