Consistent and stubborn patterns of unequal divisions of labor within heterosexual couples exist across the globe. This chapter explains why this is still the case, using the general perspective on micro-macro links in rigorous sociology and paying attention to different key mechanisms that could be driving the division of labor. Micro perspectives consider either the socio-economic status of both partners (new home economics and relative resource models) or gender roles. Macro conditions include economic circumstances, policies, culture and general gender equality in a country. Despite an impressive body of research on the division of labor, studies seem to have stalled. A new step in both theories and findings, is to get informed by studies on atypical different-sex couples, as well as from studying same-sex couples. Apart from more inclusive populations and longitudinal studies, we conclude that there is also a need for more experimental designs and more rigorous testing of hypotheses on mechanisms.