Biomarkers are enjoying increased research and use, propelling new utility in the practice of medicine and drug development. Biomarkers have driven basic principles through advances in policy and practice, engendering controversy along the way. Over the past decade, biomarker research and use have greatly expanded, along with their regulatory importance and impact on medical practice and policy. This issue of Clinical Pharmacology & Therapeutics is focused on the expanding scope of biomarker research, policy developments, and important implications for practice, as well as evolving controversies. Read Janet Woodcock's Macroscopy on regulatory opportunities for biomarkers.
  The cover image is a small section of a heat map visualizing patterns of gene expression as a biomarker for growth factor treatment in cancer cell lines (see Loboda et al. in this issue). Genes shown in magenta were upregulated by growth-factor stimulation; genes shown in cyan were downregulated. Cover designed by Erin Dewalt.