This is a little off-topic, but take a look at this link: http://learn.genetics.utah.edu/content/begin/cells/scale/ A visual way to understand scale and the size of small things without having to use analogies.
Since I’m already off topic, here is another thing that I came upon that is quite amazing: I had heard about Caledonia crows before, where they use the road and cars to crack nuts, but these rooks are creepy smart. Tool-using and a bit of Archimedes in there as well.
Bad Engineering 