<button popovertarget="my-tooltip">
  <p>?</p>
</button>

<div id="my-tooltip" class="tooltip" popover>
  <p>I am a tooltip with more information. I am a tooltip with more information. I am a tooltip with more information. I am a tooltip with more information.<p>
</div>

/* The demo */
button {
  anchor-name: --question-mark;
}

#my-tooltip {
  inset: auto;
  position-anchor: --question-mark;
  /*  Position bottom of anchored elem at top of anchor  */
  left: anchor(right);
  /*  If no space on left, swap to the right  */
  position-try-options: flip-inline;
  /*  Centering  */
  align-self: anchor-center;
  /*  set max height of the tooltip to 2x height of the anchor  */
  max-height: calc(anchor-size(block) * 2);
  max-width: 300px;
  border: 1px solid black;
}

/* Misc styling */

button {
  background: #ddd;
  font-size: 1rem;
  font-weight: 800;
  font-family: monospace;
  border-radius: 100%;
  aspect-ratio: 1/1;
  width: 1.5rem;
  line-height: 0;
  border: 2px solid black;
  margin-top: 40dvh;
  width: 2rem;
}

.tooltip {
  font-family: system-ui, sans-serif;
  background: #333;
  color: white;
  font-weight: 400;
  padding: 1rem;
  line-height: 1.5;
}

body {
  display: grid;
  grid-template-rows: 1fr;
  justify-content: center;
  height: 100vh;
}