Scientists started developing tissue-clearing methods about 15 years ago, mainly for tracing whole-brain nerve connections. A Scripps Research team has devised a novel technique that uses a sequential combination of organic solvents and water-based detergents, and makes use of water-based hydrogels to protect those molecules within the tissue that need to be preserved. It often does not require the pumping of solvents through the sample.
The development of solvent- and polymer-based brain-clearing techniques have advanced our ability to visualize the mammalian nervous system in three dimensions took 15 years and it is still in development.