JSFiddle - React, Tailwind, and code Playground

HTML

<button>Button</button>
<div class="arrow"></div>

CSS

.arrow {
    width: 0;
    height: 0;
    border-left: 10px solid transparent;
    border-right: 10px solid transparent;
    border-top: 10px solid #000;
    margin-left: 15px;
}
button:hover + .arrow {
    display: block;
}