Nanotechnology was defined by the National Nanotechnology Initiative as the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing properties of matter. The definition of nanotechnology is inclusive of all types of research and technologies that deal with these special properties. It is therefore common to see the plural form "nanotechnologies" as well as "nanoscale technologies" to refer to the broad range of research and applications whose common trait is size. An earlier description of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabrication of macroscale products, also now referred to as molecular nanotechnology.

अतिसूक्ष्मतंत्रज्ञान ही उपयोजित शास्त्राची आणि तंत्रज्ञानाची एक शाखा आहे. ह्यात प्रामुख्याने अणू अथवा रेणूंच्या आकाराइतक्या सूक्ष्म प्रमाणावर पदार्थांच्या नियंत्रणाचा अभ्यास होतो. पदार्थांचे साधारणपणे १ ते १०० नॅनोमीटर एवढ्या लहान प्रमाणात नियंत्रण करण्यासाठी अतिसूक्ष्म आकारातील साधने तयार करणे याचाही समावेश यात होतो.