MatterControl is a computer program that allows you to control a large part of the 3D-printing workflow. Using a 3D printer is still a little complex. In some ways, the word printing is a little unfortunate, because analogies with 2D paper printing are a little misleading and can lead to assumptions that somehow you just click a Print button somewhere and get a physical object out. The reality is that it is more similar to cooking, and that you need to do a bit of tweaking and know what you are doing, at least a little. MatterControl tries to hide some of the idiosyncrasies of the different printers by having a common user interface. This chapter provides an introduction into what MatterControl does (and also what it does not do) so that you can see how it fits into the overall 3D-printing workflow. We will do a quick walk through all the functionality and then subsequent chapters will go through each aspect in detail.