What do Lisp, Prolog, Tcl, machine code, and XSLT have in common? It's a computer science-y word that sounds cool and lends an academic sheen to your programming language, but do you know what "homoiconicity" really means? Maybe you saw some Scheme in college, but S-expressions aren't just about macros. This talk will demonstrate the power that comes from having the same data representation at all layers: programming language, specification, database, inter-process communication, and user interface. As examples, we will look at Clojure, a modern dynamic programming language in the Lisp family, and Datomic, a transactional, distributed database.