JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css">
<script src="http://isotope.metafizzy.co/beta/isotope.pkgd.js"></script>
<div class="box">
  <div class="row header">
    <p><b>header</b>
      <br />
      <br />(sized to content)</p>
  </div>
  <div class="row content">
  <div>
        <p>
      <b>content</b>
      (fills remaining space)
    </p>
  </div>

  </div>
  

</div>

CSS

html,
body {
  height: 100%;
  margin: 0
}

.box {
  display: flex;
  flex-flow: column;
  height: 100%;
}

.box .row {
  border: 1px dotted grey;
}

.box .row.header {
  flex: 0 1 auto;
  /* The above is shorthand for:
  flex-grow: 0,
  flex-shrink: 1,
  flex-basis: auto
  */
}

.box .row.content {
  flex: 1 1 auto;
  background: red
}


.box .row.content div {
  display: flex;
   align-self:  flex-end;
}
.box .row.footer {
  flex: 0 1 40px;
}