Iron is the most abundant transition metal on earth, and it is likely to be the last one remaining when all the rest have been extracted and consumed. Iron is also an essential element in the functioning of the human body, which contains an average of approximately 6 g for a 70 kg male.¹  It is a key component of heme and as such plays an essential role in transporting dioxygen in the blood, as well as being involved at the cellular level in the production of energy and the synthesis of DNA. Indeed, ribonucleotide reductase (RR), an enzyme that catalyses an essential step in the synthesis and repair of DNA, namely the transformation of ribonucleotides into deoxyribonucleotides, has two iron atoms in its active site.²  Iron is also present in hemoproteins such as the catalases and cytochromes P450, as well as in non-heme iron enzymes that play an important role in the activation of dioxygen.^3,4  These biological activities are associated with its different degrees of oxidation, essentially iron(ii) and iron(iii), and its ability to cycle between these two stable states (ferrous and ferric). Iron is also a component of transferrin and ferritin, metalloproteins which are responsible, respectively, for the transport of free iron in biological fluids and its storage in the body. The change in state of iron from iron(ii) to iron(iii) in the presence of dioxygen is accompanied by production of reactive oxygen species (ROS) which are potentially toxic for cells. The homeostasis of iron in the cell is a key factor in their behaviour and has to be well controlled to avoid this toxic effect. It should also be noted that cancer cells require more iron than healthy cells due in part to their rapid rate of DNA synthesis.⁵