Optical clearing for multiscale biological tissues

Three-dimensional reconstruction of tissue structures is essential for biomedical research. The development of light microscopes and various fluorescent labeling techniques provides powerful tools for this motivation. However, optical imaging depth suffers from strong light scattering due to inherent heterogeneity of biological tissues. Tissue optical clearing technology provides a distinct solution and permits us to image large volumes with high resolution. Until now, various clearing methods have been developed. In this study, from the perspective of the end users, we review in vitro tissue optical clearing techniques based on the sample features in terms of size and age, enumerate the methods suitable for immunostaining and lipophilic dyes and summarize the combinations with various imaging techniques. We hope this review will be helpful for researchers to choose the most suitable clearing method from a variety of protocols to meet their specific needs.