Some of organelles of Eukaryotic cells, most notably Mitochondria and Chloroplasts, have double membranes. These are widely believed to be Endosymbionts. Nuclei also have double membrane, but it's usually not considered to be endosymbiotic.
Eukaryotic cells are much bigger than those of prokaryotes. The volume difference is of the order of magnitude of thousand times. The eukaryota were the most recent of the three domains to appear, and include four of the five kingdoms from more traditional taxonomy - Protista, Fungi, Plantae and Animalia - with the first paraphyletic to the others.