At the heart of Qt is the QObject and the technologies that drive this. As Qt developers we love to use signals and slots, the events, the introspection and all those other features. But how do those actually work? Surprisingly few Qt developers truly understand how the QObject systems work. And by not understanding, they fail to grasp the full potential of what this can help you with. In this talk, we will dive very deep into the belly of the beast and discuss how it actually works. You will see what moc does, how it’s related to QObject and why it’s necessary. You will learn all there is to learn about what QObject does for your objects. We will also look at the Qt event loop and see how this is related to QObject and the Qt signals. This is necessary to understand what happens to your Qt signals. And finally, we will have a discussion about how this should modify the architecture of your code, how you should modify the way you think code to best make use of Qt. The full use of Qt allows you to code self contained components – getting away from the dreaded spaghetti code. The aim of this talk is to give the developer the necessary background knowledge to make the right decisions about Qt based designs in the code. This is an updated version of the talk from 2017, where the room could have been filled twice. If you missed it then, this is your chance.