we can always convert a decimal to a fraction, by simply adding as many zeros at the bottom as there are deciamals, and lose the dot atop.
so with that mouthful, let's convert 0.000002 to a fraction. It has 6 decimals, so we'll use 6 zeros.
[tex]\bf 0.\underline{000002}\implies \cfrac{0000002}{1\underline{000000}}\implies \stackrel{\textit{two millionths}}{\cfrac{2}{1,000,000}}\impliedby \textit{2 out of 1,000,000}[/tex]