[jinto36]

A lot of this is due to advances in imaging, particularly two-photon microscopy, that enable acquiring images (and video to some extent) in live subjects, e.g. mice and rats, below the top surface of tissue. For neuroscience, you can either thin the skull or install a window, and image more than 100 microns into the brain, in live animals that are anesthetized or otherwise immobilized. Here's a nice article with an overview of two-photon for this purpose (direct PDF link): https://www.hifo.uzh.ch/research/helmchen/publication/helmch... that paper was published a while ago now, but the basics are still relevant. Two-photon played a big part in the identification of the "glymphatic system" initially as well. The Nedergaard lab does a lot of imaging, and they've built custom microscopes as well. (Source: I used to work in their department, and I'm doing my PhD work in the same building. edit: in Rochester, not at KU, though I visited there when they were first outfitting the lab space in Copenhagen.