JSFiddle - React, Tailwind, and code Playground

HTML

<div id="ss">
    <span id="left" class="pane">
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
    </span>
    <span id="right" class="pane">
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div class="line"></div>
        <div...

CSS

#ss {
    border: 1px solid black;
    width: 500px;
    height: 200px;
}
.pane {
    display: inline-block;
    overflow-x: hidden;
    overflow-y: scroll;
}
#left {
    width: 399px;
    height: 200px;
    border-right: 1px solid blue;
}
#right {
    width: 95px;
    height: 200px;
}


.line {
   border-bottom: 1px solid gray;
    width: 100%;
    height: 10px;
}