The Sistine Chapel ceiling was painted between 1508 and 1512.[35] The ceiling is a flattened barrel vault supported on twelve triangular pendentives that rise from between the windows of the chapel. The commission, as envisaged by Pope Julius II, was to adorn the pendentives with figures of the twelve apostles.[73] Michelangelo, who was reluctant to take the job, persuaded the Pope to give him a free hand in the composition.[74] The resultant scheme of decoration awed his contemporaries and has inspired other artists ever since.[75] The scheme is of nine panels illustrating episodes from the Book of Genesis, set in an architectonic frame. On the pendentives, Michelangelo replaced the proposed Apostles with Prophets and Sibyls who heralded the coming of the Messiah.[74]