Cell line development is an essential step in the manufacture of biologics:drugs derived from living organisms, such as monoclonal antibodies, recombinant proteins and vaccines. In addition to this, cell lines are vital for drug screening, toxicity testing, disease modeling and investigating gene function; in a nutshell, they represent a crucial tool in the drug discovery and development pipeline. Here, we explore the process of cell line development and its contributions to drug discovery, as well as how the field has evolved over the years and the technologies that are helping it to advance. The history of cell line development The foundations of cell line development were laid in the late 19th and early 20th century, when the practice of culturing cells first took off. In the 1880s, Wilhelm Roux, of the University of Halle (Germany), demonstrated that it was possible to keep cells alive in a saline solution. Then, in 1906, Ross Granville Harrison (Johns Hopkins University; MD, USA) cultivated frog nerve cells in test tubes containing a liquid medium composed of blood clots, saline and agar. He was also instrumental in developing the ‘hanging drop’ technique, which is still used in modern cell culture research, and involves culturing cells within a droplet of plasma on the underside of a glass slide. The decades that followed heralded a number of breakthroughs, spurred on by the introduction of aseptic technique. In 1911, for example, Alexis Carrel of the Rockefeller Institute (NY, USA) described the first 3D cell culture method when he…