Fig. 1. Energy level diagrams of nonlinear optical effect. (a) Two-photon excitation; (b) second harmonic generation

Fig. 2. Schematic diagram of breast tumor progression and tumor microenvironment changes. (a) Normal breast tissue and surrounding microenvironment; (b) breast tumor progression process; (c) surrounding microenvironment of invasive breast tumor

Fig. 3. Multiphoton microscopy images of main components in tumor microenvironment

Fig. 4. Schematic diagrams of 8 relative spatial distribution patterns of tumor cells and extracellular matrix collagen fibers and corresponding MPM images, scale is 500 µm^[20]. (a) Relative spatial distribution pattern; (b) MPM images

Fig. 5. Schematic of extracting TACS corresponding microscopy features (TCMF)^[30]. (a) Interception of a region of interest; (b) extraction of four types of TCMF

Fig. 6. Relative spatial distribution patterns of three important components of tumor microenvironment: tumor cells, lymphocytes and extracellular matrix collagen fibers and corresponding MPM images, scale is 500 µm^[34]. (a) Relative spatial distribution pattern; (b) MPM images