Embryology research. These computer monitors are displaying results from a confocal microscope, used to view zebrafish embryos that have been injected with the photoconvertible fluorescent tracer Kaede. Kaede is a naturally fluorescent protein cloned from stony coral that appears to have no toxicity when expressed in zebrafish embryos. Under UV light it can be converted to a very stable form of the protein that fluoresces red and readily diffuses throughout cells, thus labelling all cell processes such as axons and dendrites (nerve fibres). It is therefore a very useful non-invasive tool for cell tracking experiments in the zebrafish embryos.