It was in Seibersdorf last summer that a scientist analysing dust taken from a cotton swipe used inside facilities in Iran discovered evidence of highly-enriched uranium - the key component of an atomic bomb. It was the first hint of a programme that had remained hidden for 18 years.
Like DNA from a crime scene, analysis of these particles also provides vital clues to the source of any nuclear material. Each radioactive isotope has its own signature.
http://observer.guardian.co.uk/international/story/0,6903,1125614,00.html