On February 6, 2010, Satoshi responds to a question from a bitcointalk user about the divisibility of bitcoin.
"Ultimately, with 6.8 billion people, there will be only 21 million coins if the project really grows. But don't worry, we have 6 more decimal places at our disposal that are not displayed by default, for a total of 8 decimal places. The wallet shows 1.00, but in reality, it's 1.00000000. If we witness significant deflation, the program can display more decimal places."