A combination of small-angle neutron scattering (SANS), conductivity, and surface tension measurements is used to show that the primary droplets in miniemulsion polymerization have the same size and the same size distribution as the final particles. It is also shown that hexadecane employed as a cosurfactant is homogeneously dispersed in the droplets find does not possess any interface activity. The presented data support that a 1 : 1 copy from monomer droplets to polymer particles is achieved.