Fig. 1. Device diagrams of digital holographic microscope^[23]. (a) In-line DHM (transmission mode); (b) off-axis DHM (transmission mode); (c) in-line DHM (reflection mode); (d) off-axis DHM (reflection mode)

Fig. 2. Connection and accuracy of disconnection trajectory^[62]. (a) 3D trajectory before using the algorithm; (b) 3D trajectory after algorithm connection; (c) the ratio of long and short tracks before and after the application of the algorithm; (d) the accuracy rate of the connected fragments at E. coli concentrations of 10⁵, 10⁶, 10⁷, 3×10⁷ CFU·mL^-1

Fig. 3. MSD of bacterial motion trajectories and screening of bacterial mobility^[64]. (a) Motion trajectories of highly motile and their corresponding MSD-Δt curves; (b) motion trajectories of poorly motile B. subtilis and their corresponding MSD-Δt curves; (c) histogram of the MSD index υ of the motion trajectories of E. coli

Fig. 4. Characteristic movement track of bacteria^[65]. (a) Characteristic movement track of wild-type E.coli HCB1; (b) characteristic motion track ofPseudomonas.sp; (c) frequency of tumble in wild-type E.coli HCB1; (d) frequency of flick in Pseudomonas.sp

Fig. 5. iSCAT optical microscope. (a) iSCAT imaging device^[84]; (b) characteristic rings of nano-scatterers at different positions^[84]; (c) 3D trajectory of a single virus particle landing on a cell membrane^[53]

Fig. 6. Data processing results of holograms^[87]. (a) Three-dimensional distribution of micro-nano bubbles; (b) size distribution; (c) three-dimensional motion trajectories

Fig. 7. The recording of a real turbulent particle field on the ground^[20]. (a) Reconstructed velocity vector field; (b) particle volume; (c) original hologram

Fig. 8. Three-dimensional motion trajectories and collisions near the surface of polymer brushes^[105]. (a) HCB1 approaches and collides with the PSPMA surface; (b) HCB1 collides and moves away from the PSPMA surface; (c) HCB1 approaches and collides with the PBMA surface; (d) HCB1 collides and moves away from the PBMA surface;(e) average scattered angle (θ_out) of motile E. coli cells at 0 min when they collide with the surface with tail; (f) θ_out of motile E. coli cells at 0 min when they collide with the surface with head; (g) duration of a tail collision; (h) duration of a head collision

Fig. 9. 3D trajectories of wild-type HCB1 and mutant HCB1414 cells swimming near an ITO surface^[106]. (a) HCB1 cells without the electric fields; (b) HCB1 cells under an AC electric field with T=10 s; (c) HCB1 cells under an AC electric field with T=0.1 s; (d) HCB1414 cells without the electric field; (e) HCB1414 cells under an AC electric field with T=10 s; (f) HCB1414 cells under an AC electric field with T=0.1 s

Fig. 10. Three-dimensional migration trajectory of fibrosarcoma cells covered in collagen gel, and the longitudinal axis is the digital holographic reconstruction distance^[16]

Fig. 11. Erythrocyte recording by DHM^[118]. (a) A hologram of a blood sample; (b) reconstructed phase diagram of defocus; (c) focusing phase diagram after digital refocusing; (d) unwrapped two-dimensional phase difference contour; (e) reconstructed pseudo-color 3D contour map

Fig. 12. Results of sperm movement near different surfaces^[120]. (a) Projected trajectories of human spermatozoa along the z axis near the surfaces with different topographies; (b) density profiles of actively swimming spermatozoa near surfaces with different topographies; (c) probability of motion patterns for spermatozoa swimming near surfaces with various topographies