In the metric system, you give a name to the following multiples: 10, 100, 1000, 0.1, 0.01, 0.001, and then you skip three places. So, you have
[tex] \left.\begin{array}{cc}\vdots&\vdots\\1000000&\text{mega}\\1000&\text{kilo}\\100&\text{hecto}\\10&\text{deca}\\0.1&\text{deci}\\0.01&\text{centi}\\0.001&\text{milli}\\0.000001&\text{micro}\\\vdots&\vdots\\\end{array}\right. [/tex]
And thus 0.000001 of something is a micro-something (i.e. one millionth of a certain unit)
