This image shows human melanoma cells (green with blue nuclei) growing in the brain of a 6-day-old zebrafish embryo with red-labeled blood vessels. I took this image as part of an experiment to try to determine how the gene YAP promotes metastasis by melanoma cells. I inject either empty vector control cells or cells over-expressing an activated form of YAP and then I watch them as they form tumors in the brain of zebrafish embryos over the course of 4 days. Through these experiments, I can determine which aspects of metastasis YAP is enhancing.