For in vivo studies of internal processes in an organism, body pigmentation is a considerable limitation. To circumvent this, various transparent fish models have already been generated, and are used in cancer research, among other things. In research on aging, however, these fish are rarely being used due to their relatively long lifespan of up to five years. Researchers at the Leibniz Institute on Aging – Fritz Lipmann Institute (FLI) in Jena have now succeeded, with the help of the CRISPR/Cas9 technology, in generating a transparent killifish (N. furzeri) called “klara”, which, with a maximum lifespan of only one year, is ideal for in vivo studies of age-related processes.