Thousands of college students across California are graduating this month with science degrees. Some dream of careers as researchers and professors, like the people who taught them. But women working toward doctoral degrees in science face gender barriers that can derail their progress.

Data from the National Science Foundation show the number of women earning Ph.D.s in all branches of science has trended up over the last two decades. By 2013, women made up half the doctorates awarded in life sciences. That’s the good news. The bad news is having a doctorate in any branch of science doesn’t eliminate gender bias, and the percentage of women with Ph.D.s in the physical sciences and engineering remain stubbornly low.

“What’s going on here is that the ideal worker is being defined as someone with a stay-at-home wife,” says Williams. “I call that sex discrimination, not women’s choices.”