This article describes the first truly photosynthetic animal reported; the Green Sea Slug. Cells in its digestive tract hijacks chloroplasts from algae it feeds on, preserve functionality of these chloroplasts in slug cells, and produce food by photosynthesis. Moreover, some genes important for maintaining photosynthetic function of these hijacked chloroplasts are believed to have transferred from algae to the slug genome. A good example of an organism with mixed animal-plant characteristics to describe complexities in organismal classification similar to Euglena that possess primitive animal-plant characteristics. A good example to discuss evolution as well.