Transmission electron microscopy (TEM) and laser scanning confocal microscopy (LSCM) are used to visualize the morphological evolution during spinodal decomposition (SD) of a binary polymer blend of poly(styrene-ran-butadiene) and polybutadiene with near critical composition. The mechanically homogenized samples were exposed to a temperature jump, and the time evolution of the characteristic wavenumber q(m) was recorded by time-resolved light scattering. TEM and LSCM micrographs at various stages are also presented to clarify the growing bicontinuous morphology. A real space analysis of the early stage of the spinodal decomposition is presented for the first time. Two-dimensional Fourier transformation was applied to the real space images to obtain information about the characteristic wavenumber, and the results were compared to the predictions obtained by Cahn’s linearized theory.