<div>
  <p>First paragraph</p>
  <p>Second paragraph</p>
</div>

<div class="reorder">
  <p class="second">Second paragraph</p>
  <p class="first">First paragraph</p>
</div>
.reorder {
  display: flex;
  flex-direction: column;
  margin-top: 24px;
}

.first {
  order: 1;
}

.second {
  order: 2;
}

p {
  border: 1px solid black;
  width:200px;
  margin: 0 0 8px;
} 

.reorder p {
  border: 2px solid darkblue;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.