Abstract: Tissue optical clearing methods, which transform intact opaque tissue into an optically transparent construct by reducing light scattering and then can be further combined with optical imaging technology to facilitate intact tissue organ deep optical (fluorescence/absorption) three-dimensional imaging, have been attracted increasing interest in biomedical photonics area due to their advantages compared to conventional mechanical-sectioning-based methods. This paper summarized optical clearing principles, main approaches and their current research situation and achievements in biomedicine, especially in the field of brain science. The comparison of their performance parameters and the further development challenge were also presented.

Key words: tissue optical clearing technology, transparent organization, imaging of mesoscopic biological systems, biomedical photonics