While the five categories of risk presented on this website 1 represent the most pressing current sources of existential risk, it is by no means an extensive list. Other, more speculative risks have been documented, but are currently not thought to significantly contribute to the total risk that we face.
The most widely discussed other potential source of risk is that of nanotechnology. Broadly speaking, nanotechnology is discipline of engineering and researching structures on the atomic and molecular scales. When arranged in molecularly precise structures, materials can take on enhanced properties, such as extreme strength, that far surpass the capabilities of the same material in its common state.
Having been brought into the public eye by engineer Eric Drexler in the ’80s, nanotechnology caused significant concern, as it was thought that the potentially fantastic capabilities of nanoengineered products could open the door to incredible new destructive powers. The effects of nanomaterials on ecosystems and the natural environment were, and still are, also causes for concern if the production and use of such materials were to dramatically increase and spread to the wider environment.
However, progress in nanotechnology research proceeded slower than expected and, while concerns still remain, it is not expected to pose an imminent threat 2.