Last month in Japan, a very special marmoset monkey was born--one who inherited from his parents not only their marmoset DNA, but also a jellyfish gene for green fluorescent protein (GFP) that makes both the animal and his parents glow green under fluorescent light. The monkey parents aren’t the first primates to fluoresce, but they are the first to pass a genetically engineered trait to their offspring. Scientists hope to use the approach to create animal models of neurological diseases, such as Parkinson’s, which cannot be adequately reproduced in rodents--the typical subjects of genetic engineering.