Why do we always have a ToolBar inside an AppBar in Material UI. Can we avoid one or the other? Are there principles surround each one? can we just have
<Toolbar className={classes.toolbar}>
  <div className={classes.container}>
    <CardMedia
      className={classes.media}
      image={logo}
      title="Logo"
    />
  </div>
  <Button className={classes.containerMenu} color="inherit">
    <MenuIcon className={classes.iconButton}/>
    Menu
  </Button>
</Toolbar>
and avoid the surrounding <AppBar>