Flexbox don't resize when use % for height for child div elements

Question

Currently I have these codes

.tomorrow
  display: flex

  .imagediv
    width: 100%
    height: 200px

In this case, the container class '.tomorrow' resizes itself to fit every of it's child's height.

But, in the next case, it does not resize itself anymore:

.tomorrow
  display: flex

  .imagediv
    width: 100%
    height: 100%  // the issue is right here

Is there any way that we can make the container class '.tomorrow' fits when we put the % value into the '.imagediv' 's height? Thank you.