The relation between theology and the time dependent morphology : of a phase-separating binary blend of polystyrene and poly(vinyl methyl ether) was investigated by heating a sample from the single-phase (at 90 degrees C) into the two-phase regime (at 124 degrees C, 16 K above the LCST) and maintaining its temperature there while measuring the evolution of the dynamic moduli G’ and G", Morphological changes occurred slowly so that there was sufficient time to cycle the dynamic mechanical measurements repeatedly over five decades in frequency. The morphology was observed on length scales From 1 mm down to 1 nm by conventional optical microscopy combined with digital image analysis, Hoffmann modulation microscopy, TEM, and WISE NMR with spin diffusion. NMR shows that major compositional changes occur mostly in the first 20 min and then the composition remains constant at about 60:40 PS/PVME for the PS-rich matrix and 5:95 PS/PVME for the PVME-rich microdomains, The PVME-rich microdomains are separated by thin layers of the PS-rich phase which forms the matrix. On a larger scale, shape and geometry change during the entire experiment (42 h). The linear domain growth appears to be consistent with the theories of Siggia and Doi-Ohta. The initial increase of the dynamic moduli is attributed to the formation of highly interconnected PVME-rich and PS-rich phases during spinodal decomposition, The subsequent decrease of the values of the dynamic moduli is considered to be the result of the loss of the interconnectivity between the two phases due to the breakup of the PS-rich phase network and the coalescence of the PVME-rich domains.