JSFiddle - React, Tailwind, and code Playground

HTML

<div class="green bubble"></div>

<div class="red bubble"></div>

CSS

.bubble {
    position: relative;
    height: 75px;
    width: 100%;
    border-radius: 5px;
    margin-bottom: 20px;
}
.red.bubble {
    background-color: pink;
}
.green.bubble {
    background-color: lightgreen;
}
.bubble:before {
    position: absolute;
    content: '';
    width: 20px;
    height: 20px;
    bottom: -10px;
    margin: 0 50%;
    background-color: inherit;
    -webkit-transform: rotate(45deg);
}