Total human height is about the diameter of Pollux.

Some say the Eridanus Supervoid is a gateway to a parallel universe.  As gateways go it is a little large at 5000000000000000000000000 meters in diameter and it is slightly cooler than the rest of the universe at -270.5 degrees centigrade.  At 25 nanometers a modern computer chip transistor gate is a less than half the diameter of a Human Immuno Virus (HIV).  A strange quark is about twice the diameter of a charm quark and strangely it is 50 times as massive as an up quark whilst being less than half the size.  The holes in spacetime foam are possibly the smallest thing known to humanity at about 0.000000000000000000000000000000000001 meters.

All this and more is beautifully illustrated in a zooming animation by Cary and Michael Huang on their htwins.net site at http://htwins.net/scale2/

And to top it all off they have included the very civilised Russell Teapot.