In this chapter, we looked at the built-in collection types Julia has to offer. We saw the power of matrices, the elegance of dictionaries, and the usefulness of tuples and sets. However, to dig deeper into the fabric of Julia, we need to learn how to define new types, another concept necessary to organize the code. We must know how types can be constructed, and how they are used in multiple dispatch. This is the main topic of the next chapter, where we will also see modules, which serve to organize code, but at an even higher level than types.