A new MP2Lab-Kleptoslug Team study published in the journal PLOS Biology addresses kleptoplasty, the capacity of host organisms to retain functional chloroplasts stolen from algae. The work focused on the long-term maintenance of photosynthetically active chloroplasts in Sacoglossa sea slugs, a capability that has earned these slugs the epithets “crawling leaves” and “solar-powered sea slugs”. The paper addresses some of the mysteries of this remarkable association: Why are functional chloroplasts retained? And how is the function of stolen chloroplasts maintained without the support of the algal nucleus?