How to make child divs always fit inside parent div?

Question

My question is if there is a way, without using JavaScript, to cause child divs to extend to the borders of their parent, without exceeding those borders, when you cannot kn

Answer 1

Make sure the outermost div has the following CSS properties:

.outer {
  /* ... */
  height: auto;
  overflow: hidden;
  /* ... */
}