We report on the synthesis of nearly monodisperse phase-separated polymer latexes with a well-defined core-shell morphology. Styrene/diisopropenylbenzene and tert-butyl acrylate/ethylene glylcol-diacrylate were used for either the core or shell of the composite microgel particles. A major concern of the paper is the detailed characterization of the core-shell and inverse core-shell particles by static and dynamic light scattering, transmission electron microscopy, solid-state NMR, and the analytical ultracentrifuge. The effect of the cross-linking agent on the final phase-separated morphology is discussed and compared with theoretical predictions.