Fundamentals of Optical Microscopy -- The White Confocal - Continuous Spectral Tuning in Excitation and Emission -- SHG/THG (Second/Third Harmonic Generation) Microscopy -- Role of Scattering and Nonlinear Effects in the Illumination and the Photobleaching Distribution Profiles -- New Analytical Tools for Evaluation of Spherical Aberration in Optical Microscopy -- Improving Image Formation by Pushing the Signal to Noise Ratio -- Site-specific Labeling of Proteins in Living Cells Using Synthetic Fluorescent Dyes -- Imaging Molecular Physiology in Cells Using FRET-based Fluorescent Nanosensors -- Measuring Molecular Dynamics by FRAP, FCS and SPT -- In vitro - in-vivo Fluctuation Spectroscopies -- Interference X-ray Diffraction from Single Muscle Cells Reveals the Molecular Basis of Muscle Braking -- Low Concentration Protein Detection Using Novel SERS Devices -- Near Infrared 3-Dimensional Nonlinear Optical Monitoring of Stem Cell Differentiation -- A Correlative Microscopy: a Combination of Light and Electron Microscopy. In the last decade, fluorescence microscopy has evolved from a classical "retrospective" microscopy approach into an advanced imaging technique that allows the observation of cellular activities in living cells with increased resolution and dimensions. A bright new future has arrived as the nano era has placed a whole new array of tools in the hands of biophysicists who are keen to go deeper into the intricacies of how biological systems work. Following an introduction to the complex world of optical microscopy, this book covers topics such as the concept of white confocal, nonlinear optical microscopy, fluctuation spectroscopies, site-specific labeling of proteins in living cells, imaging molecular physiology using nanosensors, measuring molecular dynamics, muscle braking and stem cell differentiation.