During mammalian oogenesis, the primary oocyte undergoes the first meiotic division to produce two haploid cells, a large secondary oocyte and a tiny first polar body. The secondary oocyte then undergoes the second meiotic division to produce two more haploid cells, a large egg and a tiny second polar body. Thus, the three tiny cells produced during oogenesis are called polar bodies.

The primary polar body may then divide into two additional small polar bodies, resulting in a total of three or four polar bodies. These polar bodies are packed with chromosomes that are no longer needed for the formation of the egg. They do not develop any further and eventually disintegrate.

In contrast to the egg, which continues its maturation and fertilization, the polar bodies play no active role in reproduction and are eventually discarded. Their formation helps maintain the correct chromosome number in the developing embryo.