We are focused on the transport phenomena in complex liquids. We imply single-molecule fluorescence methods to determine the diffusion coefficients on nanoscopic particles and molecules, as well as viscosity experienced by those probes. Our studies allowed us to propose the length-scale dependent viscosity model valid in such complex liquids as polymers, micellar solutions, hard-sphere, protein solutions, and, most importantly, biologically relevant complex liquids – cytoplasm and nucleoplasm. We are also pursuing the analytical tools and methods for quantifying the kinetics of biochemical reactions in complex fluids.