Reactive user interfaces: A core concept for Flutter user interface
development.

An introduction to widgets: The fundamental building blocks of Flutter user
interfaces.

The rendering process: How Flutter turns UI code into pixels.

An overview of the platform embedders: The code that lets mobile and
desktop OSes execute Flutter apps.

Integrating Flutter with other code: Information about different techniques
available to Flutter apps.

Support for the web: Concluding remarks about the characteristics of
Flutter in a browser environment.

Architectural layers

Flutter is designed as an extensible, layered system. It exists as a series of
independent libraries that each depend on the underlying layer. No layer has
privileged access to the layer below, and every part of the framework level is
designed to be optional and replaceable.