Technology Review writes: "RainDance, a startup based in Lexington, MA, aims to fill that gap with its droplet-based microfluidics technology. Founded in 2004, the company uses picoliter-sized droplets as tiny test tubes to carry out chemical reactions at very small volumes. Precisely sized droplets are created on a microfluidics chip by surrounding aqueous liquid with small volumes of oil. The droplets, generated at a rate of 10 million per hour, can be tightly packed and injected with different reagents, including strands of DNA. To catalyze a reaction, an electrical signal triggers droplets containing different reagents to merge."