There's no need to start rereading Brave New World just yet. But this week's announcement that biologists in Japan have grown mouse egg cells entirely in a lab dish gave new meaning to the term "test tube babies." The eggs, generated in a dish from two kinds of stem cells, gave rise to pups after being fertilized and implanted into rodent foster mothers. Beyond offering researchers a new way to study egg development, the feat suggests that scientists could someday make human eggs in the lab from almost any type of cell, including genetically altered ones. That may spark hope of new infertility treatments, but will also likely revive fears among those opposed to designer babies.