Zebrafish are a popular option in basic biomedical research; this piece from This Week @ USCD gives an overview of one such research program: "Embryonic stem cell researchers are trying to coax pluripotent cells down a particular lineage. In order to do this efficiently and reproducibly, both of which are critical requirements of clinical use, one must fully understand the cues that cause cells to commit to one particular fate. ... Attempting stem cell therapy without this understanding could lead to a failure of therapy, or worse, an uncontrolled growth of cells commonly known as cancer. ... Current evidence suggests that most major organ systems are replenished by tissue-specific stem cell populations. However, at this point, the scientific community does not have enough information regarding the stem cell basis of every organ system to know if adult stem cells can be used instead of embryonic stem cells."