Metal immobilization away from metabolically active sites within the cell represents the last step in both the homeostasis of metals and the detoxification of metal in excess. Assessment of the importance of this step requires having access to the in vivo speciation of metals. Evolving techniques have made it possible to acquire more reliable in situ profiling of: (i) spatio-temporal accumulation of metal, (ii) characterization of the metal-ligands complexes and determination of the structure of the different bio-ligands involved. The chapter ”metal immobilization: where and how?” presents the role of different metal-chelators in plants, based on examples from works using non-invasive techniques and genetic approaches at both the whole plant, cellular and subcellular levels. The aim of the chapter is to give a survey of the key molecules and processes involved in metal immobilization in plants, on the basis of direct and robust evidences of the in vivo speciation of metals.