Problems of aggregation and division arise in many contexts involving land and other resources.  For example, eminent domain involves the forcible assembly of land; in other instances, resources that are currently co-owned must be split up among claimants.  This talk, based on a portion of Lee Fennell’s new book Slices and Lumps: Division and Aggregation in Law and Life (University of Chicago Press, 2019) will emphasize that these two types of problems—assembly and division—are not distinct, as is usually assumed, nor is one inherently harder to solve than the other.  Instead, they share a common structure.  Through a series of examples, we will examine that structure, see what makes reconfiguration harder or easier to achieve, and consider potential solutions.