Size of mouse!
[I am big fan of jokes in 'Kids - as they see it' section in Readers Digest. Here is one gem from there.]
“Trying to explain to our five-year-old daughter how much computers had changed, my husband pointed to our brand-new personal computer and told her that when he was in college, a computer with the same amount of power would have been the size of a house.
Wide-eyed, our daughter asked, “How big was the mouse?”
Courtesy: Readers Digest