Fuel-producing microbes long seemed more like a sci-fi pipe dream than a viable solution to the fossil-fuel crisis. Then, last summer, biologist Craig Venter's upstart company Synthetic Genomics announced a $600 million collaboration with ExxonMobil to engineer strains of super-algae capable of churning out huge quantities of biofuel. Exxon is placing a massive bet that Venter--best known for his contributions to sequencing the human genome--is also ahead of the curve in the energy sector. Full-scale commercial production of Venter's algal fuel is still years away, but there are plenty of reasons for optimism: Even wild-type algae can produce about 10 times more fuel per planted acre than conventional biofuel crops such as corn and canola. Once Venter adds genes that optimize the microbe's oil production, renewable fuel under $2 per gallon could be in the making.