The power of the confocal light microscope lies in its ability to collect images, often called optical sections, at discrete levels and at different excitation wavelengths from intact fluorescently labeled biological specimens. Moreover, the registration between optical sections is preserved so that subsequent digital analysis and display are facilitated. Significant improvements have been made in recent years to the instrumentation for collecting optical sections from fixed or living biological samples labeled with one or more fluorescent probes. In addition to the laser scanning confocal microscope, the multiple photon microscope, the spinning disk microscope and deconvolution of wide field light microscope images are now practical options for imaging.