Live Cell Optical Microscopy with Limited Light Dose: Methods and applications: 2.1. Cell cultivation; 2.2. Wide-field microscopy; 2.3. Confocal laser scanning microscopy; 2.4. Light-sheet fluorescence microscopy; 2.5. Structured illumination microscopy; 2.6. Axial tomography; 2.7. Total internal reflection fluorescence microscopy; 2.8. Spectral imaging, FLIM, and FRET