//Method 1: muidocs-icon-github is defined in a style sheet.
<IconButton iconClassName="muidocs-icon-custom-github" tooltip="GitHub"/>
//Method 2: ActionGrade is a component created using mui.SvgIcon.
<IconButton tooltip="Star" touch={true}>
  <ActionGrade/>
</IconButton>
//Method 3: Manually creating a mui.FontIcon component within
IconButton
<IconButton tooltip="Sort" disabled={true}>
  <FontIcon className="muidocs-icon-custom-sort"/>
</IconButton>
//Method 4: Using Google material-icons
 <IconButton iconClassName="material-icons" tooltipPosition="bottom-center"
  tooltip="Sky">settings_system_daydream</IconButton>
