For almost any experiment that involves a light microscope, quantitative data to test a hypothesis may be obtained by microphotometry. Add a photometer and a few accessories to a light microscope, and it may be possible to quantify a cytochemical reaction product, measure the spectrum of a pigment, quantify natural or induced fluorescence, quantify birefringence, or map and analyze an image. But manually collecting thousands of numbers is unbelievably tedious. The solution is obvious. Use a personal computer (PC) to collect the numbers.