JSFiddle - React, Tailwind, and code Playground

HTML

<div class="circle"></div>

CSS

.circle {
    background: #efefef;
    border-radius: 100%;
    width: 100px;
    height: 100px;
    -webkit-transform: scale(0.5, 0.5);
    -webkit-animation: pulsing 2s infinite; /* IE 10+ */
}

@-webkit-keyframes pulsing {
  0%   { -webkit-transform: scale(0.5, 0.5)}
  50% { -webkit-transform: scale(1.0, 1.0); }
  100%   { -webkit-transform: scale(0.5, 0.5);}
}