Some embodiments include methods of forming memory cells. Heater structures are formed over an array of electrical nodes, and phase change material is formed across the heater structures. The phase change material is patterned into a plurality of confined structures, with the confined structures being in one-to-one correspondence with the heater structures and being spaced from one another by one or more insulative materials that entirely laterally surround each of the confined structures. Some embodiments include memory arrays having heater structures over an array of electrical nodes. Confined phase change material structures are over the heater structures and in one-to-one correspondence with the heater structures. The confined phase change material structures are spaced from one another by one or more insulative materials that entirely laterally surround each of the confined phase change material structures.