Modulation of a molecules targeting efficacy by modifying its substituting groups forms the molecular foundation of drug discovery.Similar modifications on nanoparticles surface ligands also alter receptors nanoparticle targets and the binding affinity.Such a human control of nanoparticles biological activity is demonstrated by three examples related to altering receptor bindings involved in immune response,tuning cell differentiation efficiency through modulating BMP signaling pathway,and regulating cell autophagy all by surface modified carbon nanotubes.Our findings not only reveal molecular interactions involved in cellular perturbations by nanoparticles,they also lay a solid foundation for safe nanomaterial design and future medicinal applications.