Button.js

import styles from './styles.scss';

...

render() {
  return (
    <a className={styles.root}>
      <span className={styles.icon}>😀</span>
      {children}
    </a>   
  );
}

Button.scss

.root {
  display: block;
  background: #ccc;
}

.icon {
  margin-right: 16px;
}