The kilogram is the basic unit of mass. It is the only basic unit (out of 7 basic SI units) which is still defined on the basis of a "prototype". The article reviews proposals to change this unpleasant situation.
http://www.physicsweb.org/articles/news/9/3/6/1
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
