In this article, you will learn how to develop real-time web apps with Firebase and Firestore. In addition, you will learn how to use (and why to use) Auth0 as the authentication system in your Firebase apps. To get your feet wet on these technologies and on the integration, you will build a simple real-time web chat that will securely store messages on Firestore (a real-time database provided by Firebase), and that will enable users to authenticate through Auth0.