When you send a message to an object in Ruby, which method is really invoked? This seemingly innocent and simple question lies at the heart of Ruby development; if you understand the difference between objects, classes, and singleton classes, then you’re doing quite well. However, understanding the relationships among these various objects can be difficult and/or challenging.  In this talk, Jay McGavren explains what happens when you invoke a method in Ruby — who receives it, what they do with it, and where that message might go. If you’re a Ruby developer but are struggling to understand the object model, including such things as “include” and “extend,” then this talk will help to bring some order to your mental model.