Here, we profiled breast tissues from over 100 women with diverse biological states (parity, menopause, age, ethnicity), which has identified 12 major cell types and over 60 biological cell states. These cell types and cell states are spatially organized into four major areas of the breast: ductal, lobular, adipose and connective regions. Our analysis has revealed abundant pericyte, endothelial and immune cell populations in normal breast, as well as highly diverse luminal epithelial cell states. Our spatial mapping using multiple technologies revealed an unexpectedly rich ecosystem of tissue-resident immune cells in the ducts and lobules, as well as distinct epithelial cell state differences between ductal and lobular regions. Collectively, these data provide an unprecedented reference of adult normal breast tissue for studying mammary biology and disease states such as breast cancer.