Exploring various transport-simulation methods and applications for properties of nanometer-scale systems, this account illustrates how quantum mechanics have become an increasingly important field of scientific research. Beginning with a short review of quantum transport, followed by various calculation methods for nanosystems based on scattering approaches, non-equilibrium Green's function, master equation, and time-dependent wave-packet diffusion, this report broaches all aspects of nanosystems, from the fundamental to more advanced topics. With numerous examples that describe quantum transport calculations, this is an essential resource for promoting an easier understanding for graduate students and researchers of the field.