JSFiddle - React, Tailwind, and code Playground

HTML

<div id="gravatar">
    <div id="circle"></div>
    <div id="square"></div>
</div>

CSS

#gravatar
{
    float: left;
}

#circle
{
    background-color: blue;
    float: left;
    height: 40px; 
    width: 40px;
    border-radius: 20px;
}

#square
{
    background-color: red;
    float: left;
    margin-left: 10px;
    height: 0;
    width: 0;
    opacity: 0;
    
    /* hover OFF */
    -webkit-transition: opacity 1s 0 ease-in-out, height 0s 1s ease, width 0s 1s ease;
    -moz-transition: opacity 1s 0 ease-in-out, height 0s 1s ease, width 0s 1s ease;
    -o-transition: opacity 1s 0 ease-in-out, height 0s 1s ease, width 0s 1s ease;
    -ms-transition: opacity 1s 0 ease-in-out, height 0s 1s ease, width 0s 1s ease;
    transition: opacity 1s 0 ease-in-out, height 0s 1s ease, width 0s 1s ease;
}

#square:hover,
#circle:hover + #square
{
    height: 40px;
    width: 40px;
    opacity: 1;
    
    /* hover ON */
    -webkit-transition: opacity 1s 0 ease-in-out, height 0 0 ease, width 0 0 ease;
    -moz-transition: opacity 1s 0 ease-in-out, height 0 0 ease, width 0 0 ease;
    -o-transition: opacity 1s 0 ease-in-out, height 0 0 ease, width 0 0 ease;
    -ms-transition: opacity 1s 0 ease-in-out, height 0 0 ease, width 0 0 ease;
    transition: opacity 1s 0 ease-in-out, height 0 0 ease, width 0 0 ease;
}