The invention includes methods for selectively etching insulative material supports relative to conductive material. The invention can include methods for selectively etching silicon nitride relative to metal nitride. The metal nitride can be in the form of containers over a semiconductor substrate, with such containers having upwardly-extending openings with lateral widths of less than or equal to about 4000 angstroms; and the silicon nitride can be in the form of a layer extending between the containers. The selective etching can comprise exposure of at least some of the silicon nitride and the containers to Cl2 to remove the exposed silicon nitride, while not removing at least the majority of the metal nitride from the containers. In subsequent processing, the containers can be incorporated into capacitors.