Before reading on, we must warn you that your next 20 minutes should be free, because once you discover the Flash tool "Scale of the Universe", that's just about the amount of time you'll need before you'll be able to focus on other things. Its goal is to help put the universe into perspective, size-wise, from top-to-bottom. If you like having your mind blown, then this tool should be right up your alley.
Crafted by brothers Cary and Michael Huang, the tool starts out rather unassuming. There's a human, a Dodo bird and a beach ball. It's not until you grab the slider bar down below that you really see what this is made of. Drag it left, and you zoom into smaller and smaller objects - slide it right, and the vice versa occurs.
Here's the best part: every single object you see can be clicked to view a description and its exact size (just because a human is beside a beach ball doesn't mean they're actually properly scaled that way, so clicking on each will give you a better idea as to the actual sizes). On the path to the bottom, you'll pass things like Transistor gates, the HIV virus, X-Ray wavelength and Proton, while upwards, you'll soar past earth, the sun, the Milky Way galaxy and ultimately reach the peak of the observable universe.
We've seen many cool things on the Internet in our day, but this has to rank up there as one of the coolest.