The gender gap in general educational attainment has reversed in most of the European Union and other advanced economies, as more young women go to university than men. Yet, significant gender gaps persist in educational choices and across fields of study. Gender gaps persist in the STEM fields of science, technology, engineering and mathematics. These gaps emerge early in secondary school and then widen further along the educational trajectory, leading to gender-specific segregation in the labour market. Understanding what causes the persistence of these gender differences, and how the causes differ at each educational stage is critical, and has implications for gender equality as well as for the allocation of talent and the overall competitiveness of countries. Given the nature and magnitude of the gender gaps, and the fact that they alter by educational stage, different policies and interventions are needed along the educational trajectory.