Some embodiments include memory cells which contain, in order; a first electrode material, a first metal oxide material, a second metal oxide material, and a second electrode material. The first metal oxide material has at least two regions which differ in oxygen concentration relative to one another. One of the regions is a first region and another is a second region. The first region is closer to the first electrode material than the second region, and has a greater oxygen concentration than the second region. The second metal oxide material includes a different metal than the first metal oxide material. Some embodiments include methods of forming memory cells in which oxygen is substantially irreversibly transferred from a region of a metal oxide material to an oxygen-sink material. The oxygen transfer creates a difference in oxygen concentration within one region of the metal oxide material relative to another.