Single cells are building blocks of all living organisms. Understanding of functions of individual live cells and their communications is essential to rationally design effective diagnosis and therapy. New tools for detecting and targeting specific individual cells would revolutionize disease diagnosis and treatments. Current tools are unable to real-time study and control molecular machineries of single live cells with adequate quantitation, spatial and temporal resolutions and over an extended period of time. We have pioneered the development of a set of powerful new nanobiotechnologies, including photostable single plasmonic nanoparticle imaging probes, single molecular assays, single molecule nanoparticle optical biosensors (SMNOBS), and far-field photostable optical nanoscopy (PHOTON). We have demonstrated that these new tools can overcome the drawbacks of fluorescence-based imaging platforms for dynamic, single molecule and multiplexing imaging of single live cells with superior temporal and spatial resolutions and over a desired extended period of time (hours, days, weeks). We have used these new tools to real-time study: (i) molecular cascades of signaling transduction pathways of single live cells, (ii) molecular mechanisms of multidrug resistance of single live cells, (iii) efficacies of individual drug nanocarriers, and (iv) native environments of developing embryos. In this keynote presentation, I will describe these new nanobiotechnologies and their innovative biomedical applications. The work has been supported by NIH and NSF.