Vital Dye Staining
In this type of method, a piece of agar or cellophane soaked in the solution of a vital dye (Neutral Red, Nile Blue Sulphate, and Bismarck Brown etc.) is applied to the surface of embryo at the needed position. The dye diffuses from agar (or cellophane) to the cells of the embryo at that position. The embryo carries on to develop normally. The stained blastomeres and their descendent cells take the dye for quite a long time and there is little or no diffusion from them to non-stained cells. The final position of stained cells in the later differentiated embryo points out the fate of the originally stained blastomeres. With this type of method the detailed fate maps of amphibian blastula and some other embryonic stages have been made.