The nuclear envelope separates the nuclear contents from the cytoplasm, also controlling a constant and massive molecular interchange between the two compartments. So why do eukaryotes go to this trouble when prokaryotes like bacteria have no such partitioning yet reproduce themselves at such amazing rates? Successful as they are, at least in terms of numbers, bacteria can be considered essentially ‘one trick ponies’. They have reached their limit as simple single cells, despite reproducing prolifically, and retaining sufficient genetic variability to consistently (and unfortunately) produce antibiotic-resistant strains. If the total number of organisms on the planet is equated with success, then bacteria come out on top. Conversely, in terms of biological complexity, they are also the most simple and consequently ‘primitive’ organisms on the planet. Bacteria also are the oldest at some four billion years, and as such provided the raw material for all subsequent life. The largest step in the evolution of living things on earth was the switch from prokaryotic to eukaryotic cell organization, i.e. the acquisition of a nucleus containing genetic material inside an isolating membrane. This has led to the proliferation and immense variation of life as we know it today. Just how the nucleus was acquired is uncertain, but it was probably as a result of phagocytosis of a small bacterium by a larger one. The smaller bacterium then ‘took over’ control of the larger one or endosymbiosis occurred with the partitioning of the DNA inside a membrane. Although cell biology is generally in agreement about the origin of mitochondria and chloroplasts by engulfment, no such consensus exists for the origin of the nucleus.