"i.e. much smaller than the width of a human hair. Picture a millimetre, then try to imagine this divided into a thousand parts (as a metre is divided into a thousand millimetres). If you've got a good imagination, you might have just managed to visualise a micrometre. To get to a nanometre you have to divide by a thousand again. If you think you've managed to visualise that, apply for a job with Steven Spielberg or make an appointment with your psychiatrist." CMP-Cientifica
