JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mybox"><center>This will be my tooltip</center></div>

CSS

#mybox {
    width:200px;   
    height:30px;
    border-style:solid;
    border-width:thin;
    border-color:#000066;
    border-radius: 4px; 
    position:relative;
}

#mybox:after {
    content:"";
    border-color: #000066 transparent transparent;
    border-style:solid;
    border-width:10px;
    width:0;
    height:0;
    position:absolute;
    bottom:-20px;
    left:20px
}