For more than a decade, the default way of building UIs in Android has been by using the View system, with XML layouts and imperative code. Recently, Google announced Jetpack Compose and that library is now the recommended way of building UI on Android: it allows the developer to be more productive and write more powerful code more intuitively. When using Jetpack Compose, the developer needs to learn how to write declarative code, instead of imperative code, as before. In this talk, we're going to give a brief overview of what is Jetpack Compose and how it changes the way we build UI on Android. We're also going to go a bit deeper in how it works and learn some best practices. Finally, we're going to present the journey of adopting Jetpack Compose in an existing app and what were the main challenges while doing it.