React

HTML

<div id="app"></div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

div.flex {
  display: grid;
  grid-template-columns: 50% 50%;
}

div.left::-webkit-scrollbar {
  display: none;
}

div.left {
  display: flex;
  flex-direction: column;
  top: 0;
  height: 92vh;
  overflow-y: scroll;
  -ms-overflow-style: none;
  scrollbar-width: none;
  justify-content: flex-start;
  z-index: 0;
}

div.right::-webkit-scrollbar {
  display: none;
}


div.right {
  position: relative;
  display: flex;
  flex-direction: column;
  top: 0;
  height: 92vh;
  overflow-y: scroll;
  overflow-x: visible;
  -ms-overflow-style: none;
  scrollbar-width: none;
  justify-content: flex-start;
  z-index: 1;
}

div.flex>div>div {
  border: 2px solid #E0E0E0;
  background-color: #F5F4F2;
  border-radius: 15px;
  margin: 10px;
  padding: 10px 40px;
  min-width: 80%;
}

#header {
  display: flex;
  position: relative;
  border: none;
  margin: 0px;
  padding: 0px;
  overflow: visible;
}

div.tooltip {
  display: none;
  position: absolute;
  border-radius: 12px;
  background: #E8E6DE;
  box-shadow: 0px 4px 11.9px 8px rgba(0, 0, 0, 0.25);
  z-index: 3;
  padding: 25px;
  width: 35vw;
  right: 100%;
}

p.label:hover>div.tooltip {
  font-size: 16px;
  display: inline-block;
  padding: 10px 25px;
}

React

class Columns extends React.Component {  
  render() {
    return (
      <div className='flex'>
         <div className='left'>
           <div>
             <div></div>
           </div>
         </div>
         <div className='right'>
           <div>
             <div id="header">
               <p className="label">
                 label
                 <div className='tooltip'>
                   <p>tooltip</p>
                 </div>
               </p>
             </div>
           </div>
         </div>
      </div>
    )
  }
}

ReactDOM.render(<Columns />, document.querySelector("#app"))