Sagittal section of a Short-Tailed Opossum (Monodelphis domestica) at 14 days after birth. One of the final steps in the visualizing process we started here and here.  Fluorescent immunostaining for muscle (red), nerve tissue (green), and cell nuclei to visualize the outlines of the animal (blue). Check out those whisker pits!  Image credit: Curious Sengi.