The endosymbiotic theory states that the some cellular organelles present inside the Eukaryotic cells were once free-living prokaryotic organisms. The eukaryotic cells ingested these organisms and over time they developed a symbiotic relationship with each other. These organelles include the mitochondria and the chloroplasts. Both these organelles contain their own DNA, and produce energy.
Hence, the answer is 'mitochondria and chloroplasts'.
