In a method of operating a memory device having a cross point array structure, the memory device includes multiple tiles, and each of the tiles includes memory cells of multiple layers. The method includes accessing, in a first tile, multiple memory cells of a first layer disposed in a region where at least one first line and at least one second line cross each other, accessing, in the first tile, multiple memory cells of a second layer disposed in a region where at least one first line and at least one second line cross each other, and accessing, after the memory cells of the multiple layers of the first tile are accessed, multiple memory cells included in a second tile. Related memory devices and memory systems are also discussed.