When you start a new app, the first thing that you do is create the models that represent your database structure. We are assuming that you have already created Django apps, or, at the very least, have read and understood the official Django tutorial. In this chapter, you will see a few interesting techniques that will make your database structure consistent across the different apps in your project. Then, you will see how to handle the internationalization of the data in your database. After that, you will learn how to avoid circular dependencies in your models and how to set database constraints. At the end of the chapter, you will see how to use migrations to change your database structure during the process of development.