Plants, algae and some bacteria are able to perform photosynthesis, which is the process of transforming sunlight energy into sugar. Animals are generally unable to use this process to acquire energy, but there are a few known exceptions to this. Some sea slugs take up chloroplasts from the algae that they consume into their cells. These chloroplasts retain their ability to perform photosynthetic activity within the animal cells for several months, and thus provide them with photosynthesis-derived nutrition. This process is called 'kleptoplasty', and it has attracted much attention due to its amazing uniqueness in making animals photosynthetic for over 50 years.