Understanding of CRuby source code has profound effects on every Ruby developer. In my talk, I will show you how to build Ruby from source. I will explain how to install and configure your new Ruby build on Mac and Linux. I will walk you through CRuby source code and introduce you to a few of the most important CRuby files. I will show you how to hack CRuby and modify some of the fundament Ruby classes in C. I will demonstrate how to write complete Ruby classes in C. Finally, I will show you that CRuby code can run 100 times faster than Ruby code. I hope that this talk will inspire you to learn more about CRuby and hack it on your own.