There are now three official dialects of Clojure. Each of them is made up of a compiler and a library of data structures, functions, and macros. ClojureScript is the first dialect of Clojure which has a compiler that's written in Clojure. In this talk I'll dig into how that compiler works, including some of the unusual details of macro expansion. I'll also discuss the data structures provided with ClojureScript, how they differ from the other dialects, and how they may improve in the future. The talk will contain forward-looking statements, which are subject to certain risks and uncertainties that could cause actual results to differ materially from those projected.