Bootstrap CSS class .align-items-*-center

<div class="d-flex align-items-center">
  <div class="p-2">Flex item 1</div>
  <div class="p-2">Flex item 2</div>
  <div class="p-2">Flex item 3</div>
</div>

<!-- responsive variations -->
<div class="d-flex align-items-sm-center">...</div>
<div class="d-flex align-items-md-center">...</div>
<div class="d-flex align-items-lg-center">...</div>
<div class="d-flex align-items-xl-center">...</div>