 Wealthy people began to build up personal libraries; Philip the Bold probably had the largest personal library of his time in the mid-15th century, is estimated to have had about 600 illuminated manuscripts, whilst a number of his friends and relations had several dozen.Up to the 12th century, most manuscripts were produced in monasteries in order to add to the library or after receiving a commission from a wealthy patron.Larger monasteries often contained separate areas for the monks who specialized in the production of manuscripts called a scriptorium.