Yesterday, I noticed Mattias' fingernails were really long and dirty.
"Hey, Bud, remind me to cut those fingernails when we get home. They're pretty long and dirty." I told him.
When we got home, he went to wash his hands. He came out of the bathroom and exclaimed,
"Mom! I know why my fingernails are so long! When I wash my hands, they get water. Dirt and water makes fingernails grow!"