Kaede is a photoconvertible fluorescence protein that changes from green to red upon exposure to violet light. The photoconversion of intracellular Kaede has no effect on cellular function. Using transgenic mice expressing the Kaede protein, we demonstrated that movement of cells with the photoconverted Kaede protein could be monitored from lymphoid organs to other tissues as well as from skin to the draining lymph node. Analysis of the kinetics of cellular movement revealed that each subset of cells in the lymph node, such as CD4⁺ T, CD8⁺ T, B, and dendritic cells, has a distinct migration pattern in vivo. Thus, the Kaede transgenic mouse system would be an ideal tool to monitor precise cellular movement in vivo at different stages of immune response to pathogens as well as in autoimmune diseases.