Figure 2.

Procedures of CLARITY. Step 1: Tissues are fixed with formaldehyde and acrylamide monomers, during which covalent links are formed between the natural molecules and monomers. Then, acrylamide monomers polymerize into a nanoporous hydrogel mesh with thermal initiation. Step 2: Lipids of tissue are eluted by an SDS detergent, with electric fields or gentle shaking applied. Tissue structure and biomolecules are preserved. Step 3: Cleared tissues may be stained with different labels. If the tissues have an endogenous transgenic expression of fluorophores, proceed directly to step 4. Step 4: Labeled tissues are incubated in RI-matching solutions to achieve homogeneity. Step 5: Tissues of interest become optically transparent and enable examination with microscopes.