This pioneering work on a non-immunoglobulin based framework for affinity protein development was first described in 1995. The new molecules were called affibodies and were based on combinatorial protein engineering of the small and robust a-helical structure of the domains of protein A. Affibody binding proteins have since then found broad use as selective binding reagents in biotechnology applications incl. for example separomics, diagnostics, viral retargeting and in vivo imaging (see refs below). Structures of affibody-target co-complexes have been solved by both x-ray crystallography and NMR. In parallel to the use of phage display technology, new selection systems for affibody libraries have also been developed both based on Gram positive bacteria, FACS-sorting of micro beads and protein fragment complementation assays (PCA).