The Mesolens microscope (left) contains a scanning system with two large beryllium mirrors (top; the mirror on the right can be seen side-on), a scan lens (black and silver cylinders), the Mesolens (two black cylinders, black cube and lower black cylinder), and a stage system to translate and focus the specimen (at the base). The Mesolens (which is 550 mm in length) is an immersion lens, and matching the immersion medium to the optical properties of the specimen greatly reduces spherical aberration, which is a common problem in light microscopy. The Mesolens design also incorporates corrections for both flat-field and chromatic aberration over a range of wavelengths. Image of a 12.5 day old mouse embryo (right); the field-of-view is 5 mm for the main image, and 0.46 mm for the inset; see Figure 5 of McConnell et al. for more details. Images courtesy of David Blatchford (left) and Johanna Trägårdh (right).