Vertical:

div {
  display: -webkit-flex;
  display: flex;
  align-items: center;
}

<div>
  Your text here.
</div>

---------

Horizontal:

div {
  display: -webkit-flex;
  display: flex;
  align-items: center;
  justify-content: center;
}

<div>
  Your text here.
</div>