The basic stages characterizing research of brood chambers (ovicells) in cheilostome bryozoans are reviewed, from their first description by J. Ellis in 1755 up to the present. The problems concerning contradictory views of researchers on the structure, formation, and function of ovicells are considered in detail. Special attention was paid to the development of modern terminology. Based on recent data, including paleontological data, the prospects are displayed of studying brood structures in Cheilostomata in order to better understand the phylogeny and evolution of their reproductive strategies.