This honor is reserved for layers.
Pixels are the basic stuff of layers, and layers are stacked to make images.
This constitutes a hierarchy of scale. Pixels are small, which makes them too hard to work with. On the other hand, whole images are too unwieldy to work with comfortably. There are conceptual parts or particular components of images we want to work with without disturbing the rest. By constructing an image out of layers, it is possible to work with each component independently of the rest of the image.