“…18 , ribosome display 19,20 , cellsurface display, bacterial two-hybrid, functional colony screening, protein-fragment complementation 21 , SELEX 22 for aptamer selection and combinations of these methods 23 will be compared taking into account the molecular entity being selected and the intended downstream applications (Box 2). For example, if affinity is crucial, technologies with built-in evolution will be required (for example, ribosome display 24 ), whereas if only 'some binder at some epitope' is needed, more technologies become available and selection is less stringent.…”