English: Self-assembled arrays and mesocrystals formed by the cubic iron oxide nanoparticles. (left) High resolution scanning electron microscopy (SEM) image of an ordered array of nanocubes taken from top-surfaces of self-assembled mesocrystals. Scale bar: 100 nm. The image has been FFT-filtered for clarity. (middle) Reflected light microscopy image of cuboidal mesocrystals composed of nanocubes by a conventional drop-casting procedure. (right) TEM image of a multilayer of nanocubes. Scale bar: 50 nm.