Limits to growth. Some groups have begun to abandon full database enumeration, preferring instead to work in building block space . Our group, with its commitment to our approach to molecular docking, currently requires enumerated databases. Fortunately, software such as Arthor and Smallworld has allowed us to continue to index and offer rapid public search within multi-10-billion databases. We think our new modular design of ZINC-22 will allow us to grow the database by another log or two, above a trillion molecules but perhaps not ten trillion. This cannot go on forever. We acknowledge the logic of avoiding full database enumeration using unenumerated combinatorial spaces . Still, we believe there are reasons to continue full database enumeration as long as we are able. Work from our lab suggests that as the database grows, docking can identify ever-better-fitting molecules .