"To measure is to know", said Lord Kelvin (1824-1907). With the intense recent interest in nanotechnology, this phrase is as apposite now as it was then. Nanotechnotogists are trying to understand things at scales we humans have trouble even fathoming. How can we quantify something that we cannot see with the naked eye, and, moreover, how do we determine its effects on things around us? (C) 2009 Elsevier Ltd. All. rights reserved.