Many philosophers are aware of the paradoxes of set theory (e.g.Russell's paradox). For many people, these were solved by the iterative conception of set which holds that sets are formed in stages by collecting sets available at previous stages.This Element will examine possibilities for articulating this solution.In particular, the author argues that there are different kinds of iterative conception, and it's open which of them (if any) is the best.Along the way, the author hopes to make some of the underlying mathematical and philosophical ideas behind tricky bits of the philosophy of set theory clear for philosophers more widely and make their relationships to some other questions in philosophy perspicuous.