JSFiddle - React, Tailwind, and code Playground

HTML

<div class="popup" style="background: red; border-color: red;"><img src="pic_mountain.jpg" alt="Mountain View" style="width:304px;height:228px;">University</div>

CSS

.popup {
    margin: 10px;
    padding: 25px;
    position: relative;
    width:50px;
    
}
.popup:after {
    content: "";
    position: absolute;
   top: 100%;
   left: 20px;
   border-top: 20px solid blue;
   border-top-color: inherit; 
   border-left: 20px solid transparent;
   border-right: 20px solid transparent; 
}