A number of large-scale and long-time molecular dynamics calculations, N=10 976 and t=1 ns, have been performed for the supercritical Lennard-Jones fluid at various densities along an isotherm at T = 1.03T(c) in order to investigate the structure and dynamics of clusters formed in the fluid as well as the fluid itself. The calculations successfully demonstrated both Ornstein-Zernike behavior of structure factor at small k region and critical slowing down in dynamic structure factor near the critical density. A molecular based picture for these phenomena in real space has been presented by newly defining several statistical mechanical correlation functions and distribution functions. A few static and dynamic properties of clusters such as generation and annihilation dynamics and single particle and collective energy fluctuations are also given.