The homeostasis of the essential transition metals copper, iron, manganese and zinc requires balanced activities of transporters that mediate import into the cell, distribution to organelles and export from the cell. Transcriptional control is important for the regulation of cellular homeostasis. In the case of Fe and Cu much progress has been made in uncovering the regulatory networks that mediate homeostasis, and key transcription factors have now been described. A master regulator of Cu homeostasis in Arabidopsis thaliana, AtSPL7, is related to the Chlamydomonas master regulator CCR1, suggesting that the key switch is conserved between the two systems even though different sets of targets are regulated in the two systems.