Ultramicroscopy is a microscopical technique that allows optical sectioning and 3D reconstruction of biological and medical specimens. While in confocal microscopy specimen size is limited to several hundred micrometers at best, using ultramicroscopy even centimeter sized objects like whole mouse embryos can be reconstructed with micrometer resolution. This is possible by using a combination of a clearing procedure and the principle of lightsheet illumination. We present ultramicroscopic 3D reconstructions of whole immunohistochemically labelled mouse embryos and adult Drosophila, giving detailed insight into their anatomy. Its speed and simplicity makes ultramicroscopy ideally suited for high-throughput phenotype screening of transgenic mice and thus will benefit the investigation of disease models.