<div class="tooltip" data-tooltip="This is a tip">Hover me for a tip!</div>

.tooltip {
  font-size: 4rem;
  margin: 5rem;
  position: relative;
}
.tooltip::before {
  content: "";
  position: absolute;
  top: -0.4em;
  left: 0.5em;
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 0.4em 0.4em 0 0.4em;
  border-color: #e5e5e5 transparent transparent transparent;
  opacity: 0;
  transition: opacity 0.3s ease-in-out;
}
.tooltip::after {
  content: attr(data-tooltip);
  position: absolute;
  left: 0;
  top: -2.2em;
  font-size: 0.5em;
  background: #e5e5e5;
  border-radius: 0.5em;
  padding: 0.25em 0.5em;
  opacity: 0;
  transition: opacity 0.3s ease-in-out;
}
.tooltip:hover::before,
.tooltip:hover::after {
  opacity: 1;
}