The core-shell structure of a spherical latex particle has been generally recognized, wherein a core usually made of cross-linked polymer chains is surrounded by a layer of small surfactant molecules. Our recent studies have revealed that the hydrophobic tails of the surfactant molecules partially penetrate into the polymer core. As a continuation of this work, the present study was designed to determine the degree of penetration. Polystyrene microlatices stabilized with cetyltrimethylammonium bromide (CTAB) were used as a model system in the investigation. A combination of both static and dynamic laser light scattering (LLS) results enabled us to determine the shell thickness to be similar to (1.0 +/- 0.2) nm, which indicates that about half of the CTAB hydrophobic tail penetrates into the polystyrene core since the fully stretched length of CTAB is about 2.7 nm. This degree of penetration has been confirmed by reanalyzing our previous LLS results on the same system with a newly modified structure of spherical microemulsions.