In the past decade, the human zinc transporter 2 (ZnT2/SLC30A2) was found to be the predominant transporter mediating the translocation of zinc into breast milk in lactating mammary epithelial cells [11], involved in clinical cases of transient neonatal zinc deficiency (TNZD) [11–19]. The gene discussed is SLC30A2; the disease is zinc deficiency, transient neonatal.