What is Nanotechnology?

The scientific field of nanotechnology is still evolving, and there doesn’t seem to be one definition that everybody agrees on. It is known that nano deals with matter on a very small scale: larger than atoms but smaller than a breadcrumb. It is also known that matter at the nano scale can behave differently than bulk matter. Beyond that, individuals and groups focus on different aspects of nanotechnology.
Here are a few definitions of nanotechnology for your consideration.
The following definition is probably the most barebones and generally agreed upon:

Nanotechnology is the study and use of structures between 1 nanometer (nm) and 100 nanometers in size. To put these measurements in perspective, you would have to stack 1 billion nanometer-sized particles on top of each other to reach the height of a 1-meter-high (about 3-feet 3-inches-high) hall table. Another popular comparison is that you can fit about 80,000 nanometers in the width of a single human hair.
The next definition is from the Foresight Institute and adds a mention of the various fields of science that come into play with nanotechnology:

Structures, devices, and systems having novel properties and functions due to the arrangement of their atoms on the 1 to 100 nanometer scale. Many fields of endeavor contribute to nanotechnology, including molecular physics, materials science, chemistry, biology, computer science, electrical engineering, and mechanical engineering.

  The European Commission offers the following definition, which both repeats the fact mentioned in the previous definition that materials at the nanoscale have novel properties, and positions nano vis-à-vis its potential in the economic marketplace:
Nanotechnology is the study of phenomena and fine-tuning of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale. Products based on nanotechnology are already in use and analysts expect markets to grow by hundreds of billions of euros during this decade.

  This next definition from the National Nanotechnology Initiative adds the fact that nanotechnology involves certain activities, such as measuring and manipulating nanoscale matter:
 Nanotechnology is the understanding and control of matter at dimensions between approximately 1 and 100 nanometers, where unique phenomena enable novel applications. Encompassing nanoscale science, engineering, and technology, nanotechnology involves imaging, measuring, modeling, and manipulating matter at this length scale

 The last definition is from Thomas Theis, director of physical sciences at the IBM Watson Research Center. It offers a broader and interesting perspective of the role and value of nanotechnology in our world:
[Nanotechnology is] an upcoming economic, business, and social phenomenon. Nano-advocates argue it will revolutionize the way we live, work and communicate.

During the Middle Ages, philosophers attempted to transmute base materials into gold in a process called alchemy. While their efforts proved fruitless, the pseudoscience alchemy paved the way to the real science of chemistry. Through chemistry, we learned more about the world around us, including the fact that all matter is composed of atoms. The types of atoms and the way those atoms join together determines a substance's properties.

Nanotechnology is a multidisciplinary science that looks at how we can manipulate matter at the molecular and atomic level. To do this, we must work on the nanoscale -- a scale so small that we can't see it with a light microscope. In fact, one nanometer is just one-billionth of a meter in size. Atoms are smaller still. It's difficult to quantify an atom's size -- they don't tend to hold a particular shape. But in general, a typical atom is about one-tenth of a nanometer in diameter.