content is-vcentered

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.7.1/css/bulma.min.css">

<div class="columns">
  <div class="column is-6">
    <div class="content is-vcentered has-text-centered fixed-dimension">
      
      <h1>Content</h1>
      <p>that might be from</p>
      <p>wysiwyg containing</p>
      <p>multiple lines, etc.</p>
    </div>

  </div>
  <div class="column is-6">

    <div class="content is-vcentered fixed-dimension">
      <p>Some text line without has-text-centered</p>
    </div>

  </div>
</div>

CSS

.fixed-dimension {
  height: 400px;
  width: 400px;
  background-color: grey;
}

/* shortcut to select content tags like p, h1, etc.  */
/* this is for the multiple lines to work */
.content > * {
  width: 100%;
  margin: 0 !important; /* not recommended */
}

.content.is-vcentered {
  display: flex;
  flex-wrap: wrap;
  align-content: center; /* commenting this out, the multiple lines will have gaps */
  align-items: center; /* commenting this out, the one-line will not align */
}