Mesoscopy is the whole imaging (3D) or large samples ranging from 1mm to a few cm, with techniques such as light-sheet microscopy (aka SPIM - Selective Plane Illumination Microscopy) or optical (projection) tomography (aka OPT), among others.
SPIM is well suited for live imaging of small embryos such as zebrafish or drosophila, less than 2mm and ~500um thick. For larger samples it is advisable to use OPT, however, in this case imaging is limited to fixed samples.
It is also possible to image fluorescence and bioluminescence in vivo using animal imagers, and have those images registered with X-ray images of the whole animal.
Mesoscopy resources are available at ALM @ i3S, BI @ i3S, AIF @ IGC, BF @ iMM, UM @ NMS-CEDOC, LMP @ CF nodes.