(A) Properties of photoconvertible molecule, caged fluorescent dye. The caged fluorescent dyes are photoconvertible molecules. The dyes are in an inactive state when conjugated with caging reagents (e.g., Bhc-diazo,DMNB) and reactivated by UV irradiation. (B) Scheme of cell trace experiment with a caged fluorescent dye. The caged fluorescent dye is injected into the 1-cell stage embryo, and then UV beams are irradiated to label the cell population in the chosen region at an appropriate stage. This method enables the visualization of cell movements.