Atoms are very, very small. Atoms are so small that it is often said that there are as many atoms in a single grain of sand as there are grains of sand on all of the world's beaches - certainly a difficult thing to prove, but you get the idea - atoms are really small. Richard Feynman was a great scientist, and he once said that "another way to remember their size is this - if an apple is magnified to the size of the earth, then the atoms in the apple are approximately the size of the original apple."