In much the same way that some kids play with Legos, some scientists play with BioBricks—that is, interchangeable biological components that can be used to build synthetic biology devices and systems. (Why build block castles when you can build living things?!) The Registry of Standard Biological Parts, founded at MIT, is a catalog of such biological building blocks. It is interesting to browse, as it reads like a car part catalog. Each component class (such as promoters, terminators, and protein-coding sequences) has a designated symbol, and visitors to the site can browse these classes. Alternatively, one can browse the parts and devices by function, such as biosynthesis, cell death, and viral vectors. The Registry is a must-visit site for synthetic biologists, as well as anyone with a curiosity for what makes living organisms tick.