The sharpest object in the world is a tungsten needle with a tip just one atom wide, making it the sharpest man-made object ever created

. This tungsten nanoneedle was developed by scientists at the National Institute for Nanotechnology and the University of Alberta and is recognized by the Guinness World Records

. Its tip radius is so small that it cannot be made any thinner, essentially one atom thick

. However, despite its extreme sharpness in terms of geometry, this tungsten nanoneedle cannot actually cut or pierce anything because it is extremely brittle and would break under pressure

. Thus, while it holds the record for sharpness by atomic scale, it is not functional as a cutting tool. In practical terms, some of the sharpest cutting tools used are obsidian blades, which have an edge radius of about 3 nanometers-thinner than a strand of DNA

. These obsidian blades have been used since the Stone Age and are still employed in certain surgeries today because their ultra-sharp edges allow for precise cuts with minimal pressure, such as in delicate eye surgeries

. In summary:

• Sharpest object by atomic scale: Tungsten nanoneedle with a one-atom-wide tip (world record holder)

• Sharpest practical cutting edge: Obsidian blades with edges about 3 nanometers thick, used in surgery for their precision

• Note: Sharpness depends on both geometry and functionality; the tungsten nanoneedle is sharper in scale but not usable for cutting

This illustrates that "sharpness" can be defined differently depending on whether you consider just the physical tip size or the ability to cut effectively.