Abstract The aim of this article is to provide a comprehensive and consistent overview of structural transitions during polymerization of high internal phase emulsions (HIPEs). The obtained polymerized HIPEs (known as polyHIPEs) usually have an interconnected porous structure consisting of pores (also called voids) and interconnecting holes, known as pore throats (or windows). We describe how emulsification process and stability of HIPEs affect the pore size of polyHIPEs. The pore throat size is mainly controlled by the interdroplet interaction (affecting flattened area and interdroplet layer thickness between neighboring droplets as well as the interdroplet layer drainage) and interfacial film strength. The processing and molding of polyHIPEs are evaluated from rheological and chemorheological behaviors. It is also discussed how the porogen effect of surfactants, polymerization-induced phase separation, and crystallization induce heterogeneity in polymer phase of polyHIPEs.