Um, 1 billionth of a meter is 1 nm. Saying it's 200 nm (like the paper says) is very different from saying it's 1 billionth of a meter (like the linked article incorrectly says).

I thought convention in SI units was to drop down a level when at less than 1 of a unit..?

A pretty common approach (at least in Canada) is to use prefixes at intervals of 1000 - mm, m, km and then larger unit to one decimal for large values - 700m as 0.7km, 0.9l instead on 900ml, and so-on.

you'll rarely see cl, dg, or hm used here.

Though it's almost unheard of now, a british billion = 1000 * a british million. In that context it does hold, being 2 british billionths of a metre thick.

That said, here we all bascially use the American 'billion' because it makes a more logical approach and allows for dealing with larger numbers more easily.

I thought it used to be: a british billion is a million million i.e. 1,000,000,000,000.

Thus a british billion is 1000 * an american billion.

Nowadays we use the american billion of 1,000,000,000.

Pretty sure we all agree that a million is a thousand thousand.

Wow I screwed up big time. I meant to say it was a million million and I have no idea why I said otehrwise. I'm going to blame tiredness. Thanks for the correction.