Self-assembly
![Electron microscopy image of an iron oxide nanoparticle. Regularly arranged dots within the dashed border are Fe atoms. Left inset is the corresponding electron diffraction pattern. Scale bar: 10 nm.[1]](/uploads/202502/10/Iron_oxide_nanocube4859.jpg)
![STM image of self-assembled Br4-pyrene molecules on Au(111) surface (top) and its model (bottom; pink spheres are Br atoms).[2]](/uploads/202502/10/Br4Py_self-assembly_on_Au4859.jpg)

![The DNA structure at left (schematic shown) will self-assemble into the structure visualized by atomic force microscopy at right. Image from Strong.[3]](/uploads/202502/10/DNA_nanostructures4859.png)
Self-assembly is a process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction. When the constitutive components are molecules, the process is termed molecular self-assembly.