Ever wondered how a language runtime like the CLR really works but never had the courage to peruse all of the runtime code on GitHub? Then this hands-on workshop is for you! Come join us for a full day of building a miniature version of the CLR, supporting a reduced Intermediate Language (IL) instruction set with a rudimentary type system. During this workshop, we'll build a loader for small IL-based programs, craft an interpreter for a reduced IL instruction set, and build a basic mark-and-sweep compacting garbage collector. Once we get some trivial programs to run, we'll add on extra features such as instance methods, virtual dispatch, and exception handling. After completing this crash course in language runtimes, many of the once mysterious concepts around instruction sets, control flow, interpreters and JIT compilers, automatic memory management, etc. will have become clear and tangible.