Abstract: Methods, systems, devices and apparatus for use in screening and/or selecting a library of nucleic acid molecules and/or nucleic acid tagged or encoded molecules for binding to or interaction with a target molecule or substance (e.g., for use in new compound or drug discovery) are described. In some embodiments the device comprises: (a) a spatially addressable array, said array comprising a plurality of separate and discrete locations thereon; (b) a plurality of different oligomers operably connected to said spatially addressable array at different ones of said separate and discrete locations; (c) a tag sequence which is complementary to, and is hybridized to, each of said oligomers; and (d) a candidate chemical operably connected to each of said tag sequences, wherein each of said discrete locations is a unique identifier for its corresponding oligomer; and wherein said tag sequence is a unique identifier for its connected candidate chemical.