Many tissues, especially those with a rapid turnover, such as the lining of the gut, the blood-forming tissues, the hair follicle, and the germline cells, are renewed by means of stem cells. These adult stem cells are found in a few specific anatomic locations in the tissue, known as niches. Stem cell niche refers to a microenvironment in regulating decisions of stem cells between self-renewal and differentiation. In this lecture, I will introduce a paper that shows niches of germline stem cells in the Drosophila ovary, and we will learn what cells are a key niche component and how they maintain stem cells.