Molly's Cat.

When Mollys pet cat dies, Mollys tears turn to wonder and eventually joy, as she finds out about atoms and how the atoms of her cat will be reused and become part of other plants and creatures in the future.

In this journey of discovery, she realises that if the atoms continually get reused in the future, then they must have also done so in the past, and she speculates about what famous people or intriguing creatures may have once used the atoms that she now possesses.

This leads her to wonder where these atoms came from in the first place, and she skips for joy and she is amazed when she discovers the answer.