JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/LeaVerou/prefixfree/gh-pages/prefixfree.min.js"></script>
<div class="speech-bubble">
    Content
</div>

CSS

.speech-bubble {
    background: #999;
    background: linear-gradient(top, #444 0%,#999 100%);
    background-clip: padding-box;
    border: 5px solid rgba(0, 0, 0, 0.2);
    padding: 20px;
    width: 200px;
    height: 100px;
    position: relative;
}
.speech-bubble:before{
    content: ' ';
    border-color: rgba(0, 0, 0, 0.2) transparent transparent;
    border-style: solid;
    border-width: 17px;
    position: absolute;
    bottom: -39px;
    left: 16px;
}
.speech-bubble:after{
    content: ' ';
    border-color: #999 transparent transparent;
    border-style: solid;
    border-width: 13px;
    position: absolute;
    bottom: -26px;
    left: 20px;
}



















































body {
    padding: 20px;
    background-color: #026873;
    background-image: linear-gradient(0, rgba(255,255,255,.07) 50%, transparent 50%),
      linear-gradient(0, rgba(255,255,255,.13) 50%, transparent 50%),
      linear-gradient(0, transparent 50%, rgba(255,255,255,.17) 50%),
      linear-gradient(0, transparent 50%, rgba(255,255,255,.19) 50%);
    background-size: 13px, 29px, 37px, 53px;
    /* Included to show that the border is indeed semi-transparent */
    /* http://lea.verou.me/css3patterns/#cicada-stripes */
}