Biological circuits have been a reality for years. However, making them is no mean feat: you typically have to create everything from scratch, which is impractical for everyone but a specialized genetic engineer. MIT has a better way, though. It developed a programming language that makes it comparatively easy to produce these organic machines -- you just write code (based on existing computer instructions) and get a bacteria-friendly DNA sequence that does what you want. In the lab, sample circuits in E. coli did everything from ranking inputs to measuring oxygen levels.