Simultaneous measurements of mRNA and protein abundance and turnover in mammalian cells, have revealed that a significant portion of the cellular proteome is controlled by mRNA translation. Then, what molecular machinery do cells execute for translational regulation? It has become increasingly clear that proper cellular control of pluripotency and differentiation is related to the regulation of ribosome synthesis. In this lecture, I will introduce the paper that shows how ribosomes are regulated and functions on germ-line stem cell differentiation, and we will learn the unique important step of translational regulation.