Confocal fluorescence microscopy, while an improvement in image resolution over conventional widefield fluorescence, is still limited in terms of depth for much thicker samples. Excitation light is absorbed and scattered as it penetrates cells and tissue, and the resolution decreases with greater depth. With “Two-photon” or “Multiphoton” microscopy, two photons are fired near simultaneously in order to excite a very fine focal point within a sample. All of the light detected is then emitted from only the small focal point, and the out-of-focus light is effectively removed. Scanning of all the points across the sample then allows for the construction of a high resolution 3D image. Thus, multiphoton microscopy is very well suited for a number of important applications that require imaging of samples with a thickness of 200 micrometers up to several millimeters. Most notably, it can image the fine cellular detail inside of living animals, such as in the neurons, lymph nodes and blood vessels of mice, and even entire sections of zebrafish.