body {
  margin: 0;
  font-family: sans-serif;
}

main {
  height: 100vh;
  display: grid;
  grid-template-areas:
    'aside header'
    'aside content';
  grid-template-rows: 50px 1fr;
  grid-template-columns: auto 1fr;
}

header {
  grid-area: header;
  background-color: lightslategray;
    text-align: center;
}

aside {
    grid-area: aside;
}

article {
  grid-area: content;
  background-color: lightgray;
    overflow-y:scroll;
    padding:1em !important;
}