Monoclonal Antibodies (MABs) are antibodies that are made by identical immune cells, cloned from a single parent cell. They are therefore of constant structure and bind to the same foreign markers (called “antigens”). The technology behind the generation of monoclonal antibodies was discovered in 1972 by César Milstein and Georges Köhler – scientists at the Roche-funded Basel Institute for Immunology – who were later to win the Nobel Prize. Monoclonal antibodies revolutionized biological research and built the basis for the use of therapeutic antibodies in medicine and for the entire biotechnology industry. At Roche, we use different approaches to generate libraries of MABs to a specific antigen. Besides living organisms, we also deploy an vitro technology, antibody phage display, to generate antibodies. Here, the antibody diversity is generated in a DNA encoded library in vitro that will lead to the display of a large collection of human antibody molecules on the surface of cultured cells. Subsequent selection and screening steps with an antigen of choice towards this pool of cells leads to the isolation of high affinity binders. In vitro display technologies allow targeting specific properties, like the antibody response on certain predefined part of the antigen.