What is nano?

To begin, "nano" is actually a prefix that comes from the Greek word for dwarf.
It simply means one billionth. So, one nanometer (1 nm) is one billionth of a meter.

Extremely small : nanoid.
One-billionth : nanometer

Here is a list of metric measures to help those who are not familiar with this system.

There are three important "nano" terms to consider when you're trying to understand the
increasing news coverage and scientific developments in the field of nanotechnology.
These terms are: Nanoscale, Nanoscience and Nanotechnology.

The Nanoscale

The nanoscale is about a thousand times smaller than micro that is, about 1/80,000 of
the diameter of a human hair. Approximately 3 to 6 atoms can fit inside of a nanometer,
depending on the atom. The prefix nano means ten to the minus ninth power, or one
billionth.Nanoscale technologies are the development and use of devices that have a
size of only a few nanometres. Nanotechnologists manipulate single molecules and atoms.

How small is a nanometer?

It's defined as one billionth of a meter. How small is that?
Some ways to think about just how small a nanometer is:

• A sheet of paper is about 100,000 nanometers thick.
• Blond hair is probably 15,000 to 50,000 nanometers in diameter,
  but black hair is likely to be between 50,000 and 180,000 nanometers.
• There are 25,400,000 nanometers in an inch.
• A nanometer is a millionth of a millimeter.
• A ping pong is proportional to the earth

Definitions of the word "Nano"

Merriam-Webster's Collegiate Dictionary

Definition: Nano technology
Function: noun
Date: 1987
Glossary: The art of manipulating materials on an atomic or molecular scale especially
to build microscopic devices (as robots).
Engines of Creation
Nanotechnology - technology based on the manipulation of individual atoms
and molecules to build structures to complex, atomic specifications.

The About.com

Definition at the physics portal: 
Nanotechnology Definition: The development and use of devices that have
a size of only a few nanometres. Research has been carried out into very
small components, which depend on electronic effects and may involve
movement of a countable number of electrons in their action. Such
| devices would act faster than larger components. Considerable interest
has been shown in the production of structures on a molecular level by
suitable sequences of chemical reactions. It is also possible to manipulate
individual atoms on surfaces using a variant of the atomic force microscope.

Webopedia's

Definition of nanotechnology
A field of science whose goal is to control individual atoms and molecules
to create computer chips and other devices that are thousands of times
smaller than current technologies permit. Current manufacturing
processes use lithography to imprint circuits on semiconductor materials.
While lithography has improved dramatically over the last two decades --
to the point where some manufacturing plants can produce circuits smaller
than one micron (1,000 nanometers) -- it still deals with aggregates of
millions of atoms. It is widely believed that lithography is quickly approaching
its physical limits. To continue reducing the size of semiconductors, new
technologies that juggle individual atoms will be necessary. This is the
realm of nanotechnology. Although research in this field dates back to
Richard P. Feynman's classic talk in 1959, the term nanotechnology was
first coined by K. Eric Drexler in 1986 in the book Engines of Creation.
In the popular press, the term nanotechnology is sometimes used to refer
to any sub-micron process, including lithography. Because of this, many
scientists are beginning to use the term molecular nanotechnology when
talking about true nanotechnology at the molecular level.

Whatisit.com

Nanotechnology, or, as it is sometimes called, molecular manufacturing,
is a branch of engineering that deals with the design and manufacture of
extremely small electronic circuits and mechanical devices built at the
molecular level of matter. The Institute of Nanotechnology in the U.K.
expresses it as "science and technology where dimensions and tolerances
in the range of 0.1 nanometer (nm) to 100 nm play a critical role."
Nanotechnology is often discussed together with micro-electromechanical
systems (MEMS), a subject that usually includes nanotechnology but may
also include technologies higher than the molecular level.

There is current work being done on the nanoscale at universities, major
corporations, private starts ups and military and NASA labs. (these include
self assembled nanoparticles, nanotubes, nanorings, nanowires,
| nanocomposites, and Nadrian Seemans work at NYU which produced a
nanorobotic arm out of synthetic DNA).

The goals of the research, range from biotech applications, to nanoassemblers,
nanocomputers, and nanochips along with molecular electronics. There are
also more advanced scenarios to the potential applications of nanotechnology.
These astounding and various possibilities are estimated to happen from 5 to
30 years from now.

The work that is being done now tends to be used with atomic force microscopy,
or scanning tunneling microscopy. You may recall the IBM commercial where
their Almaden lab had pushed together some thirty odd xenon atoms to spell
out the letters IBM. This was a great achievement for the nanotech field, underlining
that, we can move them. Eventually there is aim to construct capabilities beyond
merely moving atoms around but to bind them and build atomic specified molecular
machines. The first mention of this type of tiny science was by Richard Feynman
at his famous 1959 talk. The great generator of nanotech at the time is K. Eric Drexler,
who wrote the book Engines Of Creation, and Nanosystems among others.
He is chairman of the Foresight Institute who's goal is to prepare for nanotechnology.
Foresight holds annual conferences and gatherings for its senior associates.

What is nanoscience and technology?

Nanoscience involves research to discover new behaviors and properties of
materials with dimensions at the nanoscale which ranges roughly from 1 to 100
nanometers(nm). Nanotechnology is the way discoveries made at the nanoscale
are put to work. Nanotechnology is more than throwing together a batch of
nanoscale materials¡Xit requires the ability to manipulate and control those
materials in a useful way.

What is special about the nanoscale?

In short, materials can have different properties at the nanoscale¡X some are
better at conducting electricity or heat, some are stronger, some have different
magnetic properties, and some reflect light better or change colors as their size is changed.

Surface area

Nanoscale materials also have far larger surface areas than similar volumes
of larger scale materials, meaning that more surface is available for interactions
with other materials around them.

Why surface area is important?

Compare a piece of gum chewed into a wad with stretching that gum into as
thin a sheet as possible. The surface, or area visible on the outside, is much
greater for the stretched out gum than for the wad of gum. The stretched out gum
will likely dry out and become brittle faster than the wad since the sheet has
more contact at the surface with the air moving around it.

Where is nanoscale material found?

If scientists can create artificial spider silk economically, the superstrong,
| lightweight materials could be used in sports helmets, armor, tethers
and other products. Nanoscale materials and effects are found in nature all
around us. Nature's secrets for building from the nanoscale create processes
and machinery that scientists hope to imitate. Researchers already have copied
the nanostructure of lotus leaves to create water repellent surfaces used today
to make stain-proof clothing, other fabrics, and materials. Others are trying to
imitate the strength and flexibility of spider silk, which is naturally reinforced by
nanoscale crystals.

Many important functions of living organisms take place at the nanoscale.
Our bodies and those of all animals use natural nanoscale materials, such
as proteins and other molecules, to control our bodies¡¦ many systems
and processes. A typical protein such as hemoglobin, which carries oxygen
through the bloodstream, is 5 nanometers, or 5 billionths of a meter, in diameter.

Nanoscale materials are all around us, in smoke from fire, volcanic ash, sea spray,
as well as products resulting from burning or combustion processes. Some have
been put to use for centuries. One material, nanoscale gold, was used in stained
glass and ceramics as far back as the 10th Century. But it took 10 more centuries
before high-powered microscopes and precision equipment were developed to
allow nanoscale materials to be imaged and moved around.

What is nanoscale behavior?

At the nanoscale, objects behave quite differently from those at larger scales.
Gold at the bulk scale, for instance, is an excellent conductor of heat and electricity,
but not of light. Properly structured gold nanoparticles, however, start absorbing light
and can turn that light into heat, enough heat, in fact, to act like miniature thermal
scalpels that can kill unwanted cells in the body, such as cancer cells.

Other materials can become remarkably strong when built at the nanoscale. For example,
nanoscale tubes of carbon, 1/100,000 the diameter of a human hair, are incredibly
strong. They are already being used to make bicycles, baseball bats, and some
car parts today. Some scientists think they can combine carbon nanotubes with
plastics to make composites that are far lighter, yet stronger than steel. Imagine
the fuel savings if such a material could replace all the metal in a car! Carbon
nanotubes also conduct both heat and electricity better than any metal, so they could
be used to protect airplanes from lightning strikes and to cool computer circuits.