Unlike modern cells, with their mitochondria, pores, nuclei and such, the very first cell, which emerged some 3.5 billion years ago, was simple. It probably consisted of just a membrane with genetic information inside—raising the question of how it could take in nutrients and reproduce. Harvard Medical School researchers have built a model of what the first cell may have looked like. Using fatty acids that likely existed on a primeval Earth, they created a membrane porous enough to let in nutrients but strong enough to protect the genetic material inside. In a test tube of water, the fatty acids formed into a ring around a strip of DNA. The investigators also added nucleotides—units of genetic material—which entered the cell, latched onto the DNA and replicated it over 24 hours. Scientists now must figure out how the original and copycat DNA strands can separate, which would enable the cell to divide and reproduce. The study turned up in the June 12 Nature.