What is a nanometer?

A nanometre (American spelling: nanometer, symbol: nm) is 1.0×10"9 metres — or one billionth of a metre. It is an SI measure of length, commonly used in measuring the wavelengths of visible light (400 nm to 700 nm), ultraviolet radiation and gamma rays; amongst other things.

1 nm = 1000 picometre.
1000 nm = 1 micrometre ( or 1 micron)
In older (e.g. 1958) texts, the nm is sometimes denoted "mµ" for "millimicron", based on the old term "micron" for a micrometre. Double prefixes are not allowed in SI, and this is never seen in modern writing or speech.

picometre << nanometre << micrometre

Examples of a Nanometer dimensions

Single water molecule - about 1.5 nanometers
Strand of human DNA - 2.5 nanometers in diameter
Strand of hair - about 80,000 to 100,000 nanometers wide
Sheet of paper - 100,000 nanometers thick
There are 25,400,000 nanometers in one inch
One nanometer is about as long as your fingernail grows in one second

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