how to customize style of material ui components code example

Example 1: adding style to root material ui

<Button
  classes={{
    root: classes.root, // class name, e.g. `classes-nesting-root-x`
    label: classes.label, // class name, e.g. `classes-nesting-label-x`
  }}
>
  classes nesting
</Button>

Example 2: create a common style material ui style

const styles = (theme) => ({
  cardContainer: {
    position: 'relative',
    width: '50%',
    padding: theme.spacing.unit / 2,
  },
  cardOuter: {
    height: '100%',
    width: '100%',
    textAlign: 'start',
  },
  card: {
    width: '100%',
    background: theme.palette.backgrounds.card.off,
  },
  cardOn: {
    background: theme.palette.backgrounds.card.on,
  },
  cardUnavailable: {
    background: theme.palette.backgrounds.card.disabled,
  },
  cardContent: {
    display: 'flex',
    flexWrap: 'wrap',
    minHeight: 98,
    height: 98,
    [theme.breakpoints.down('sm')]: {
      minHeight: 74,
      height: 74,
    },
    padding: `${theme.spacing.unit * 1.5}px !important`,
  },
});

export default styles;