A polyhistidine-tag (His-tag) is an amino acid motif in proteins that consists of at least six histidines and is commonly positioned at the N- or C-terminus of the protein. His-tag is a popular tag used for purification of proteins by Ni-NTA affinity chromatography. The use of this tag is nowadays extended also to surface immobilization, incorporation of active proteins in nanomaterials and Protein Labeling with biotin and Fluorophores , as with NanoTemper Technologies’ RED-tris-NTA labeling kits.