Believe it or not, creating artificial life (albeit based on existing species) isn't new. However, scientists have managed a particularly unusual feat: they've built synthetic bacteria that has the smallest known genome of any lifeform... ever. Their modification of Mycoplasma mycoides has just 473 genes, or so few that it likely couldn't survive and reproduce if you shrank the genome further. The trick was to do a better job of determining which genes were essential. Many of those that weren't deemed necessary in the past turned out to be half of a vital pair, giving researchers a good sense of what they could afford to cut.