The main results of the RFBR grant No. 20-32-70134 "Investigation of photoaging and chronological aging of skin using optical methods" (supervisor – Kulikov D.A., сo-executors - members of our laboratory) were published in the Diagnostics journal (indexed in Scopus, WoS, Q2). Kulikov D. et al. Methods of Non-Invasive In Vivo Optical Diagnostics in the Assessment of Structural Changes in the Skin Induced by Ultraviolet Exposure in an Experimental Model // Diagnostics. – 2021. – Т. 11. – №. 8. – P. 1464-1483. The study, conducted in cooperation with laboratory workers, demonstrated the possibility of using non-invasive optical methods, such as Laser Fluorescence Spectroscopy, Laser Doppler Flowmetry, Optical Tissue Oximetry, and Optical Coherence Tomography, to study and quantify the dynamic changes during photo- and chrono-aging processes in the skin. The clinical application of these results was suggested. Based on the data analysis of optical diagnosis and histological investigation of the skin, coefficient k, describing the rate of collagen degradation, which can be called an optical criterion of skin aging, was developed.