Cosimo built a room to hold them in the Convent of S.Marco, which Flavio Biondo styled the first library opened for the use of scholars.

Lorenzo the Magnificent enriched the collection with treasures acquired during his lifetime, buying autographs wherever it was possible to find them, and causing copies to be made.

In the year 1508 the friars of S.Marco sold this inestimable store of literary documents, in order to discharge the debts contracted by them during their ill-considered interference in the state affairs of the Republic.

It was purchased for the sum of 2652 ducats by the Cardinal Giovanni de' Medici, a second son of Lorenzo the Magnificent, and afterwards Pope Leo X.He transferred them to his Roman villa, where the collection was still further enlarged by all the rarities which a prince passionate for literature and reckless in expenditure could there assemble.

Leo's cousin and executor, Giulio de' Medici, Pope Clement VII., fulfilled his last wishes by transferring them to Florence, and providing the stately receptacle in which they still repose.
The task assigned to Michelangelo, when he planned the library, was not so simple as that of the new sacristy.