Fig. 1. Energy level diagram of TPEF and SHG[60]

Fig. 2. (a) SHG, (b) TPEF, (c) combined SHG (grey) and TPEF (green) images of the human esophageal stroma[25] (excitation wavelength is 850 nm, scale bar is 20 μm)

Fig. 3. Representative TPEF/SHG images of cancerous gastric mucosa and submucosa[26](scale bar is 50 μm)

Fig. 4. (a) Representative multiphoton images of normal, (b) precancerous, (c) cancerous colonic tissues at depth of 0 μm[19](scale bar is 50 μm)

Fig. 5. (a) Representative SHG images of normal, (b) precancerous, (c) cancerous colonic tissues[22] (excitation wavelength is 800 nm, image size is 415 μm×490 μm, scale bar is 50 μm)

Fig. 6. (a) SHG and multiphoton imaging of ex-vivo human dermis in 20, 40, and 70 years-old patients (blue is SHG and green is TPEF); (b) skin aging quantification of these tissues using SAAID metric[42]

Fig. 7. (a) Optical diagnosis of ex-vivo human basal cell carcinoma using MPM imaging (blue is SHG, green is TPEF); (b) adjacent H & E histological section[44]

Fig. 8. Multiphoton image across entire cornea of GFP mouse (green is TPEF, blue is SHG [53])

Fig. 9. Clinical photography (a) and multiphoton images (b) of keratitis[78]