Here is the full quotation from The Letter to Herodotus, preserved in Lives and Opinions of Eminent Philosophers by Diogenes Laertius:

“Furthermore, there are infinite worlds both like and unlike this world of ours. For the atoms being infinite in number, as was proved already, are borne on far out into space. For those atoms, which are of such nature that a world could be created out of them or made by them, have not been used up either on one world or on a limited number of worlds, nor again on all the worlds which are alike, or on those which are different from these. So that there nowhere exists an obstacle to the infinite number of the worlds.” — Epicurus

This was one of the pieces of writing that really caught my eye when discovering Epicurus. The description just seemed so modern, but was developed without any of our modern equipment or knowledge. Amazing!