Resizing Summary Block thumbnails?

My code is:

.summary-item {
  float: left !important;
  padding: 5px;
  height: 200px;
  width: 200px;
}

.summary-thumbnail {
  image-size: intrinsic !important;
}

My problem is that the container is 200 × 200, my image, however is not resizing properly to fit the content inside the container. How do I change the code so that the image fits the container and still maintains its aspect ratio without getting cropped?

I have also set the height and width to content-fit and it doesn't work either. Any suggestions? It would be greatly appreciated.