cell differentiation | male gamete generation | cellular process | multicellular organismal reproductive process | gamete generation | reproduction | reproductive process | multicellular organism development | multicellular organism reproduction | anatomical structure development | developmental process | spermatogenesis | sexual reproduction | multicellular organismal process
intracellular membrane-bounded organelle | fibrillar center | cell | nuclear lumen | nucleolus | cytoplasm | intracellular organelle | membrane-bounded organelle | nucleus | organelle | membrane-enclosed lumen | intracellular