We have used the direct energy-transfer method to study the internal morphology of a nonaqueous-dispersion-polymerization latex. These 1-μm particles contain 97 mol% poly(methyl methacrylate) (PMMA) and 3 mol% polyisobutylene (PIB). Phenanthrene (donor) and anthracene (acceptor) were doped selectively into the PIB phase. These dyes sample length scales up to 34 Å and indicate an "effective local dimension" $\overline{d}=2\mathrm{}$, a result which conveys important information about the PIB phase in this material.