JSFiddle - React, Tailwind, and code Playground

HTML

<div class="bubble">Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
</div>

CSS

.bubble {
  width: 20em;
  border: solid 1px gray;
  padding: 1em;
  margin: 1em;
  background: yellow;
  
  position: relative;
}

.bubble:before {
  content: '';
  width: 20px;
  height: 20px;
  background: yellow;
  position: absolute;
  bottom: calc(0% - 11px); /* size + border */
  left: calc(50% - 10px);  /* size */
  transform: rotate(45deg);
  border-right: solid 1px gray;
  border-bottom: solid 1px gray;
}