This September 7, the Chemical Abstracts Service registered the 50 millionth unique chemical substance, arylmethylidene heterocycle. It look CAS 33 years to register the first 10 million chemical substances in 1990, but only nine months to go from 40 million to 50 million — an indication of the accelerated pace of scientific activity. The CAS Registry database is updated daily, so you can always get an up-to-date record count. On November 24, 2009, the count was already up to 51,045,390 organic and inorganic substances.