Technologies now exist that allow a variety of assessments to be performed that were previously limited. An important contribution to today’s toolbox of imaging modalities has been the development of optical projection tomography (OPT) [1]. OPT has filled a niche for 3D imaging of cells and structures labeled with highly specific contrast agents, such as antibodies and RNA probes, in the millimeter–centimeter scale range. As such, the technology bridged an existing gap for imaging tissue specimens of a size that is frequently utilized in, for example, developmental biology and organ phenotyping in rodents.