One of the reasons I've been MIA lately is that I'm tutoring several students in biochemistry and cell biology. I recently finished explaining the theory of endosymbiosis to one of my students. That's the theory that explains the origin of eukaryotic cells - that is, mitochondria and chloroplasts, and possibly other organelles, represent formerly free-living prokaryotes that were ingested in another cell. It is supported by the fact that these organelles are double-membraned, have their own DNA, and can replicate independently of the rest of the cell. But now, a new open accessmeta-analysis has decided to shake this all up, stating that the origin of eukaryotic cells happened from the inside-out.