Illustration of the technique for producing recombinant Factor VIII from human Factor VIII genes (orange gene), used in the treatment of hemophilia. The human gene is recombined into the DNA to obtain new cells that will produce recombinant Factor VIII. The cells are conserved frozen in test tubes and make up a bank of cells that can be used to produce Factor VIII in large quantities. Cells are unfrozen, retreated and cultured in a bioreactor.