 A natural thought to have about sentences with referring nominal concrete mass expressions (e.g., “Alvin drank the water that Roderick poured” or “The coffee in that cup is too hot”) is that the expressions refer to portions of matter, which are themselves made up of smaller bits of matter. It seems obvious that thinking this is what taking such sentences at face value amounts to. Not obvious, though, is what metaphysical commitments this requires, and what metaphysical problems might come along with this thought.