Every Java developer should have a good working knowledge of JVM bytecode. Its fun, it can help you diagnose problems, improve performance, and even empowers you to build your own languages. No matter what kind of Java application you work on, youll get something out of this talk. Well start with bytecode fundamentals. Youll learn how the most common operations work and see visual representations of how the JVM executes that code. The second part of the talk will introduce Jitescript, a Java library for generating bytecode. You learn how to use Jitescript with some plain old Java code to create your own JVM languages.