There is no strict size limitation for nanotechnology, as the field encompasses a wide range of technologies and applications that manipulate matter at the nanoscale. However, the term "nanotechnology" is generally used to refer to the manipulation of matter at the atomic, molecular, and supramolecular scales. This typically involves dimensions of 1 to 100 nanometers (nm). Below this size range, the field of quantum physics becomes more relevant, and the properties and behaviors of matter can be significantly different from those at larger scales.

However, it's important to note that the boundaries of nanotechnology are not strictly defined, and there can be some overlap with other fields such as atomic and molecular physics, condensed matter physics, materials science, and more. Additionally, as technologies advance, the ability to manipulate matter at even smaller scales may become possible, expanding the size range associated with nanotechnology.