Polystyrene microgels are nanometer-sized particles produced by polymerization and crosslinking in microemulsion. As a result of their internal network structure, microgels have negligible intermolecular entanglement interactions. This can have a profound effect on their rheology; it also leads to glassy fracture resembling the behavior of low molecular weight, linear polystyrene. At higher frequencies, the mechanical response of microgels is quite similar to that of linear polystyrene. Breakdown of time-temperature superpositioning occurs in the softening zone of the viscoelastic spectrum. In the glass transition region, the segmental relaxation function is broadened and exhibits an enhanced dependence on temperature. The latter two effects, due to the cross-linking of the microgels, are also seen in conventional, macroscopic networks.