JSFiddle - React, Tailwind, and code Playground

HTML

<div class='series'>
    
    <div class='header'>123</div>
</div>

CSS

.series {
    width:200px;
    height:300px;
    background-color:red;
    z-index:999;
    
    overflow:auto;
    border: 2px solid #33ccff;
    position:absolute; 
    text-align:center;
    padding-top:30px;     
}
.header{
    height:30px;
    width:100%;
    position:fixed;
    top:0;
    left:0;
    background-color:green;
    display:inline;
}