We present a study on the structure and dynamics of poly(ethyl methacrylate) (PEMA), one of the polymers with shortest side-group in the poly(n-alkyl methacrylate)s (PnMAs) series. The contributions to the structure factor have been unveiled by combining T-dependent X-ray and neutron diffraction with polarization analysis on samples with different deuteration labelings, accessing thereby different partial structure factors of PEMA. We find clear hints for strong structural ordering with anticorrelated side-groups and main-chain locations, fitting thus in the general scenario of nanosegregation of main chains and side groups found in higher order PnMAs members. Backscattering measurements on a PEMA sample with deuterated side-group have revealed the dynamics of main-chain and alpha-methyl group hydrogens. The characterization of the rotations of the latter indicates highly disordered environments in the glassy state. Above the glass transition, the incoherent scattering function related to segmental relaxation shows stretching and clear deviations from Gaussian behavior in the accessed window. We also present results on the dynamic structure factor (collective dynamics) at the peaks characteristic (i) for the intermain-chain and interside-group-domain correlations and (ii) for the side-group/side-group atomic correlations within the domains. Viscosity dictates the temperature dependence in both cases, and also that of the dielectric spectroscopy results at high temperatures. However, the a-process followed by dielectric relaxation deviates from the rheological behavior when approaching the calorimetric glass-transition, indicating a strong influence of the faster side-group motions on the dynamics of the dielectric probes.