Optical projection tomography (OPT) is a 3D imaging technique developed by Sharpe et al. [1] in 2002, which is used for non-invasive imaging of biological samples. Typical sample sizes lie in the order of several millimeters. Analogous to X-ray computed tomography, the sample is rotated, and 2D projections of the sample are obtained at different rotation angles. A reconstruction algorithm is then used to reconstruct a 3D image from the 2D projections. Image contrast based on transmitted light, absorption, or different types of immunofluorescence-labeled structures or autofluorescence is used to identify sample features in 3D.