

<style>
.flexbox {
  background-color: lightgrey;
}
#item1 {
  vertical-align: 10px;
}
#item3 {
  vertical-align: 30px;
}
</style>

<div class='flexbox'>
  <!-- flex item: block child -->
  <div id='item1'>block</div>
  <!-- flex item: anonymous block box around inline content -->
  anonymous item 2
  <!-- flex item: inline child -->
  <span id='item3'>item 3</span>
</div>
