March is National Women’s History Month and the right time to ask: why are women still underrepresented in Science, Technology, Engineering and Mathematics (STEM)? According to a recent National Science Board report, women made up just 28 percent of science and engineering workers in 2010. They also make up less than 10 percent of the engineering workforce, according to the MIT Women’s Initiative. This lesson explores the careers of 19 great female scientists, the obstacles they overcame and asks students to look at their own schools, teachers, friends and families to see whether those obstacles continue to operate in their lives.