Visualization
Spinner
For hover, active and focus-visible states to work properly, you need to define the 'icon-root' class on the parent element (e.g. button). For custom active state, you can also use the 'active' class.
Progress Bar
In case you want to visualize the progress of a major action, the Spinner might be too subdued. In those cases, you should use this beautiful ProgressBar component.
Page Progress
You can display the page loading state with this component. It shows up at the very top pixels of the page. So it can only be used for global loading indication.