Affinity purification is based on the specific interaction of a target molecule with an immobilized ligand. Affinity technology can isolate specific molecules from a mixture, capture a desired molecule for interaction studies, or remove a component from a reaction. For recombinant proteins, the addition of fusion tags using appropriate expression vectors enables affinity purification by a number of strate-gies. Here we showcase products specifically designed for the purifica-tion or detection of fusion proteins containing His•Tag®, GST•Tag™, S•Tag™, Strep•Tag® II, HSV•Tag®, Nus•Tag™, and T7•Tag® sequences. These products are optimized for purification of proteins expressed in bacterial, yeast, insect, or mammalian systems. Reagents and kits are available in a variety of configurations, suitable for processing cultures from milliliter to liter scales in low- or high-throughput formats. For maximal recovery of intact target proteins from cell cultures, a first step in purification should be an efficient, gentle extraction. In Part 1, Protein Extraction Reagents, we describe a variety of these detergent-based and enzymatic methods for convenient lysis and protein extraction from bacterial, yeast, insect, or mammalian cells. Part 2, Protein Purification and Detection, features a variety of affinity purification platforms, which provide options for conventional column or cartridge chromatography, rapid magnetic-based separations, or filtration methods for purifying milligram quantities in a high-through-put format. Premium quality fusion tag monoclonal antibodies and Western blot kits featured in this section allow highly specific, sensitive detection of fusion proteins with antibodies directed against GST•Tag, His•Tag, HSV•Tag, Nus•Tag, S•Tag, Strep•Tag II, T7•Tag, or Trx•Tag™ sequences. After the target protein is purified, the fusion tag may be removed with one of the site-specific proteases described in Part 3, Site-specific Proteases and Cleavage Capture Kits. Key accessory prod-ucts for protein production, purification, and detection are highlighted in Part 4, Accessory Products. These products include iFOLD™ Protein Refolding Systems, D-Tube™ Dialyzers and the D-Tube Electroelution Accessory Kit, protease inhibitor cocktails, electrophoresis size stan-dards, Western blot reagents, and protein quantification kits. Finally, Part 5, Technical Tips for Recombinant Protein Purification, offers sound advice on how to improve protein purification.