How many?

Kilometres

The kilometre, or kilometer in American English, is a unit of length in the metric system, equal to one thousand metres. Many people know a marathon race is 26.2 miles long but did you know that a marathon is 42.195 in kilometres?

Micrometres

The micrometre or micrometer, also commonly known as a micron, is an SI derived unit of length equalling 1×10−6 metre; that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm, or about 0.000039 inch). The micrometre is often used to measure the thickness or diameter of microscopic objects, such as microorganisms and colloidal particles.