Branchiomerism refers to the division of the head and neck of an embryo into a series of segments, each with its own set of gill arches. Synonyms for this term can be quite varied, and some of the most common include: pharyngeal segmentation, gill arch development, brachiomeric patterning, and pharyngeal arch morphogenesis. Other related terms might include cranial segmentation, head segmentation, or even pharyngeal system development. Regardless of the specific terminology used, the process of branchiomerism is a critical part of embryonic development for a wide range of vertebrate species, and understanding this process is essential to understanding the evolution and diversity of life on Earth.