App.js

import React, { Component } from 'react';
import Header from './Header';
class App extends Component {
  render() {
    return (
      <div>
        <Header />
        <div className="columns">
          <div className="column">1</div>
          <div className="column">2</div>
        </div>
      </div>
    );
  }
}
export default App;