There are more stars in the sky than there are grains of sand on all of the beaches on Earth. Although we cant physically count them either, it has been estimated by numerous scientists to be true. To the naked eye we are unable to see the billions of stars that exist but just usually a few scattered on a clear night but beyond our sight are vast amounts of them all over the galaxy. But in a glass of water there are up to 3000 times more molecules than there are stars in the sky. Something else that cannot see with the naked eye and not really something you presume to have millions of molecules in as its just water.