Fig. 1. Schematic diagram of the point-scanning system and its typical application results. (a) Structural diagram of confocal laser scanning microscope; (b) Multicolor confocal images and 3D reconstruction of brain tissue section^[24]; (c) Single-photon and two-photon volumetric imaging of brain neurons, and imaging depths with different illumination strategies^[22]

Fig. 2. Realization of fast scanning technology and its typical application. (a) Multifocal scanning device; (b) Spinning disk multifocal scanning; (c) Fast scanning technique for real-time observation of 3D movement of the Golgi apparatus^[31]; (d) Time delayed multifocal scanning; (e) Axial scanning with tunable lens; (f) 3D functional imaging of mouse neurons through a tunable lens^[32], 180 µm× 180 µm× 165 µm, temporal resolution: 0.25 s; (g) 3D imaging result of a zebrafish embryo through multifocal structured illumination microscope. Red box indicates a dividing cell^[33]

Fig. 3. Structure of light-sheet microscope and typical volumetric imaging result. (a) Structure of traditional light-sheet microscope; (b) Volumetric imaging result of zebrafish heart^[49], including 2D image sequence (left) and 3D reconstruction (right), scale bar: 50 μm; (c) Time-lapse images of a zebrafish heart^[51], the line chart on the right is the heart beat dynamics, scale bar: 30 μm

Fig. 4. Structure of light-field microscope and typical volumetric imaging result. (a) Structure of traditional light-field microscope; (b) Typical reconstruction results at different depths of the worm brain^[59], scale bar: 50 µm; (c) Blood flow imaging at 200 Hz volumetric imaging rate^[60], 200 µm×200 µm×200 µm

Fig. 5. Structure of 3D-SIM and typical imaging result of super resolution technology. (a) Representative system structure; (b) Comparison of imaging results of fluorescent microspheres with conventional microscope (left) and 3D-SIM (right)^[76]; (c) Dynamic 3D super resolution imaging results of transferrin clusters^[80], scale bar: 50 nm; (d) Imaging results of rat hippocampal neuron^[81], including widefield imaging (left), classical super resolution optical fluctuation reconstruction (middle), and super resolution optical fluctuation reconstruction using Fourier interpolation (right)

Fig. 6. OPT system and typical 3D reconstruction results. (a) Traditional OPT system structure; (b) Fluorescent 3D reconstruction results of Drosophila melanogaster pupae^[93]

Fig. 7. Reconstruction results under limited angles or sparse sampling. (a) Results of 180° and 130° tomographic reconstruction^[103]; (b) Reconstruction results of filtered back-projection using 180 projection data(left) and reconstruction results of 2-stage deep learning network using 9 projection data^[105]