The ________ widget can be used to create custom themes for individual sections of an app.

The 'Theme' widget can be used to create custom themes for individual sections of an app in Flutter. By wrapping a section of the widget tree with a 'Theme' widget, developers can define specific aspects of the theme, such as colors, fonts, and styles, for that particular section. This allows for fine-grained theming within an app, enabling developers to create visually distinct and cohesive designs for different parts of the user interface.