Until recently, fluorescence microscopy was dominated by large microscope installations, some- times referred to as the rigs.
The observations of neural circuitry in freely moving animals like mice or rats require wearable fluorescence microscope attached to imaging cannulas chronically implanted in their brain.
To make this microscope mice-wearable, the smallest fluorescence microscope body ever was built that easily snaps into chronically implanted imaging cannula via self-centering latch- ing mechanism.
The snap-in microscope body is electrically pigtailed and optically connectorized.
In the middle of the visible spectrum, the scattering through the brain tissue limits imaging to about 150 μm.
The imaging limited to those depths from brain surface can be performed without insertion of all-glass relay lenses.
At larger brain depths, it is absolutely necessary to use relay lens systems that may consist of homogeneous or gradient-index glass rods or lenses that bring the image into focus of the microscope objective and effectively reduce the optical path through the brain tissue.