css styles example

styles-in-css.css

.thumbnail {
  margin: 5px,
  padding: 5px,
  background-color: #91969A,
  border-radius: 3px,
  min-width: 66px
}

.sponsored {
  background-color: #F9BF3B,
}

styles-in-css.js

import classNames from 'classnames'

import './style-in-css.css' // assume has the .thumbnail and .sponsored class declaration 

class Post extends React.Component {
  
  render(){
    
    // css is seperated but still need javascript
    
    const thumbnailClass = classNames({
      'thumbnail': true,
      'sponsored': this.props.post.type === 'sponsored'
    });
    
    <div>
      <div className={thumbnailClass}>
    </div> 
  }
}