div {
  margin: 0;
  padding: 0;
}

#inner-not-scrollable {
  width: 100px;
  height: 25px;
}

#inner-not-scrollable-content {
  width: 200px;
  height: 50px;
  background-color: #ccc;
}

#inner-scrollable {
  width: 100px;
  height: 50px;
  overflow: scroll;
}

#inner-scrollable-content {
  width: 600px;
  height: 1000px;
  background-color: blue;
}