Ever wondered how the Just-In-Time (JIT) compiler of the CLR turns your beautiful C#, VB, or F# code into efficient, highly optimized code at runtime, or ahead of time (AOT)? Then this deep dive talk is for you! During this talk, we'll dive into the mysterious world of code generation, optimization techniques, and how the JIT interacts with other parts of the CLR such as the loader, type system, and garbage collector (GC). Using live demos compiling code snippets and with the CLR source code handy on GitHub, we'll gain a deeper understanding of the inner workings of the JIT. After this talk, jargon like constant folding, loop unrolling, strength reduction, inlining, common subexpression elimination, vectorization, devirtualization, register allocation, tiered compilation, on-stack replacement, write barriers, etc. will no longer sound like witchcraft to you!