such as chemistry, computer science, engineering, mathematics, and physics, to illuminate principles that govern life at the molecular and cellular level. MCB also encourages research that exploits experimental and theoretical approaches and utilizes a diverse spectrum of model and non-model animals, plants, and microbes across the tree of life. Proposals that pursue potentially transformative ideas are welcome, even if these entail higher risk. This solicitation calls for proposals in research areas supported by the four MCB core clusters, including: (i) structure, dynamics, and function of biomolecules and supramolecular assemblies, especially under physiological conditions (Molecular Biophysics); (ii) organization, processing, expression, regulation, and evolution of genetic and epigenetic information (Genetic Mechanisms); (iii) cellular structure, properties, and function across broad spatiotemporal scales (Cellular Dynamics and Function); and (iv) systems and/or synthetic biology to study complex interactions through modeling or manipulation or design of living systems at the molecular-to-cellular scale (Systems and Synthetic Biology). All MCB clusters prioritize projects that integrate across scales, investigate molecular and cellular evolution, synergize experimental research with computational or mathematical modeling, and/or develop innovative, broadly applicable methods and technologies. Projects that bridge the intellectual edges between MCB clusters are welcome. Projects that integrate molecular and cellular biosciences with other subdisciplines of biology are also welcome through the new Integrative Research in Biology (IntBIO) track. Regarding health-related challenges, NSF supports basic research in all areas of the biological sciences and recognizes that this foundational research is likely to impact many different areas, including human health. MCB celebrates all the biological science discoveries funded through MCB awards that have had major impacts on health, environment, energy, food production, and other applications. Nevertheless, research focused exclusively on understanding human diseases and their treatment is normally outside of the scope offunding and will be returned without review unless that research significantly advances other fields such as engineering, computer science, or the mathematical and physical sciences.