Abstract: A microscopic technique for generating high-clarity, large volume 3D images of fluorescent tissue structure at subcellular resolution and capture transient activities. The technique includes capturing two orthogonal 2D projection of the sample volume by performing a projection scan with an excitation laser sweeping through the volume at up to 100 vps, tracking the scan depth using an electrically tuned lens to keep the emission image in focus and generate an xy plane volume projection image at the camera; and placing a PMT behind the excitation lens to collect emission passed through the excitation lens, wherein signals from the PMT form a focus scan projection at the yz plane; and then merging the xy and yz projections.