Zinc(II) is essential to life. It is involved in biological processes as cofactor of proteins, and as signalling ion. This demands a precise control of zinc movements and concentrations. In vertebrates, zinc transport across lipid bilayers is mediated principally by two protein families, ZNT (SLC30) and ZIP (SLC39). These proteins are ubiquitously present among organisms and unique insight into the mechanism of Zn2+ translocation comes from studies of the Escherichia coli SLC30 homologue, Yiip, the structure of which has been determined at 2.9 Å resolution. Here we emphasize the structure-function relationship of YiiP as it mediates the journey of Zn2+ across the membrane. Zinc also permeates cell membranes through calcium channels and, in prokaryotes, plants and fungi, by the aid of P-type ATPases. ZIP proteins can mediate gated flux of free zinc into the cytosol and the resulting zinc transients modulate cell signalling networks, and in particular pathways involved in cell proliferation, migration and differentiation. A slower genomic effect of elevated cytosolic free zinc concentrations occurs through a zinc-responsive transcription factor, MTF1. There is also a dynamic binding and release of zinc from metallothioneins that completes an intricate system to regulate this biologically active trace metal.