Luminal cells are thought to be the cells of origin for several breast cancer subtypes and as a result are the subject of intense interest among breast cancer researchers. In the past it has been difficult to study these cells because they represent a rare population among cells grown in a lab dish. To tackle this issue, Todhunter et al. tested a new way of growing these cells called “postconfluent culture.” Instead of frequently splitting dense cultures into new dishes, the authors let them grow for 2–5 weeks without any disturbance save regular media changes. This technique greatly increased the proportion of luminal cells in culture and created an environment more like the human breast. As such, postconfluent culture is a valuable tool for breast cancer researchers wanting to understand and intervene in early stages of breast cancer initiation.