Lai, H.M. et al. Nat. Commun. 9, 1066 (2018).

Tissue-clearing methods have allowed imaging-based analysis of thick tissues and even whole organisms, with the rodent brain being a particularly common sample. However, clearing methods that perform well on rodent brains do not necessarily work as well on human brain samples, owing to challenges associated with the processing of postmortem tissue and inherent differences in tissue composition. To overcome this limitation, Lai et al. developed OPTIClear, a clearing method optimized for human brain tissue. The method is compatible with fluorescent dyes and works with both fresh and archival samples, including formalin-fixed paraffin-embedded tissues, opening the door to 3D visualization of many archived materials. Using their method along with cresyl violet staining, the team was able to study human dendritic spines in 3D.