Twenty years of gender mainstreaming in international organisations (IOs) has produced an international network of gender experts and a distinctive body of expertise on gender relations. Gender experts have led the development of policies, built capacity through training, designed and implemented projects, pioneered new administrative techniques (such as gender budgeting), spearheaded innovative research, and evaluated interventions geared towards advancing gender equality and women's empowerment. In the process, they have introduced the term "gender" into international politics, built a body of knowledge about gender relations and women's subordination, and fostered the diffusion of such knowledge internationally and its translation into local contexts. They also have formed networks among each other, and they recognise each other's work. In other words, gender expertise has emerged as a professional field.