Kleptoplasty is where certain organisms "steal" chloroplasts, the organelles responsible for photosynthesis, from algae or other plants. This process allows these organisms to temporarily harness the power of photosynthesis, even though they are not naturally capable of it.

Kleptoplasty is commonly seen in some species of sea slugs, particularly in the Elysia genus. When these sea slugs consume algae, they do not fully digest the cells. Instead, they retain the chloroplasts and incorporate them into their own cells, particularly within their skin. These stolen chloroplasts can continue to function and provide energy to the host organism, sometimes for weeks or even months, allowing the sea slug to sustain itself partially or fully on photosynthesis.

However, the exact process and sustainability of kleptoplasty vary. While some organisms maintain the chloroplasts temporarily, they generally cannot repair or replicate them, as they lack the necessary genes for chloroplast maintenance. This dependency makes kleptoplasty an example of symbiosis and evolutionary adaptation.