Two main approaches are used in nanotechnology. In the "bottom-up" approach, materials and devices are built from molecular components which assemble themselves chemically by principles of molecular recognition.These seek to arrange smaller components into more complex assemblies.
In the "top-down" approach, nano-objects are constructed from larger entities without atomic-level control.These seek to create smaller devices by using larger ones to direct their assembly.
The Functional approaches seek to develop components of a desired functionality without regard to how they might be assembled. For instance, Molecular scale electronics seeks to develop molecules with useful electronic properties. These could then be used as single-molecule components in a nanoelectronic device. Also, Synthetic chemical methods can also be used to create synthetic molecular motors, such as in a so-called nanocar..
The Biomimetic approaches or Bionics or biomimicry seeks to apply biological methods and systems found in nature, to the study and design of engineering systems and modern technology. Biomineralization is one example of the systems studied.
The Speculative subfields seek to anticipate what inventions nanotechnology might yield, or attempt to propose an agenda along which inquiry might progress. These often take a big-picture view of nanotechnology, with more emphasis on its societal implications than the details of how such inventions could actually be created.