Scientists used a chemical cocktail namely “Scale”. They have found that the mixture of chemicals i.e. urea, glycerol and soap makes the membranes transparent and used the same mixture on the fetus of the mouse, which resulted in the transparency of the pigments of the cells.
This technique helped scientists to see fluorescent neurons in the brain.
Authors have written,
In Scale-treated mouse brain, neurons labeled with genetically encoded fluorescent proteins were visualized at an unprecedented depth in millimeter-scale networks and at subcellular resolution. The improved depth and scale of imaging permitted comprehensive three-dimensional reconstructions of cortical, callosal and hippocampal projections whose extent was limited only by the working distance of the objective lenses. In the intact neurogenic niche of the dentate gyrus, Scale allowed the quantitation of distances of neural stem cells to blood vessels. Our findings suggest that the Scale method will be useful for light microscopy–based connectomics of cellular networks in brain and other tissues.
This chemical not only helps in stop of change of sample or shape but also helps to avoid reducing the intensity of signals from the genetically-encoded fluorescent proteins in the tissue.
Hama, H. et. al. (2011). Scale: a chemical approach for fluorescence imaging and reconstruction of transparent mouse brain. nature Neuroscience