Twenty-year-old Rosalyn Sussman cut a steely, solitary figure in September 1941 as she started her doctorate in nuclear physics at the University of Illinois Champaign-Urbana. “I was the first woman to have a graduate assistantship in physics there since 1917,” she recounted to biographer Eugene Straus. She was the only female faculty member among 400, and there were no women’s bathrooms in the lab facilities—a major inconvenience, especially during the many nights she spent sleeping on the floor of the lab. Despite her confidence and persistence, even Rosalyn couldn’t have predicted that she would graduate several semesters early, make the jump to medicine, develop a revolutionary technique in the field of endocrinology, and win the Nobel Prize in Physiology or Medicine in 1977.

Decades later, there’s no question that Rosalyn Sussman Yalow (her married name) and Gertrude Elion, Yalow’s contemporary and fellow Nobel laureate, were trailblazers in medical research. Yalow helped develop a technique called radioimmunoassay, a highly sensitive method for measuring hormone levels in-vitro, and Elion developed many new drugs, including the precursor to the first drug to treat AIDS, AZT. They are two of only 10 women to ever win the Nobel Prize in Physiology or Medicine.

Many stories about pioneering women and minorities in science focus on their intrinsic determination to carry on in spite of setbacks. But there were two major external powers at work that helped propel Yalow and Elion. These elements—changes to the predominant, male-oriented culture around them and strong relationships with mentors across gender lines—are still highly relevant today, as women forge new paths in science, technology, engineering, and math (STEM) fields.

Although the two women’s career trajectories were starkly different—Yalow did her research at a New York City hospital, while Elion worked for the pharmaceutical company now known as GlaxoSmithKline—their backgrounds and early education were strikingly similar. Both had European-born Jewish parents who were among the 24 million immigrants that flooded America’s ports between 1871 and 1914. Both grew up in the Bronx and attended the now-defunct Walton High School. They both even matriculated to the all-female Hunter College, graduating four years apart.

Yalow and Elion didn’t come face-to-face with the male-dominated scientific world until they started looking for work and applying to graduate school. When they did encounter it, they found it more than just challenging—it was downright discriminatory.  One of the heads of the Veterans Affairs (VA) hospitals—a group that comprised the most powerful people in medicine in the early 1940s—said this of female applicants: “If she’s good looking, what is she doing in medicine? And if she’s not good looking, who wants her?” Elion herself was turned down from a job in a lab because she was “too pretty” and would be “a distracting influence.” Elion recalled, “I almost fell apart. That was the first time that I thought being a woman was a real disadvantage. I got very discouraged.”

That culture changed quickly at the start of World War II, when positions filled by men were suddenly left vacant by the draft or the draw of secretive technological research. The war also gave science a new allure; the success of the Manhattan Project made Americans hope that science could solve anything. Money poured into research and development, and Yalow and Elion were able to move up the ranks more quickly. “They had to have a war so that I could get a Ph.D. and a job in physics,” Yalow told biographer Straus. Although this window of opportunity for women largely closed once men returned from war, some women like Yalow and Elion had just enough of a foothold (plus enough drive) to continue their ascent.

Yalow and Elion also managed to find influential male mentors and research partners. In 1944, when she was 26, Elion became the assistant to George Hitchings, then the head of the biochemistry lab at the pharmaceutical company Burroughs Wellcome. Taking note of her aptitude and eagerness, Hitchings gave Elion more autonomy in the lab. The two co-authored many papers and developed several of the drugs that would eventually win them the joint Nobel Prize. Despite their differences and tensions (several of which the Prize made public), Elion acknowledged that she would never have achieved what she did without Hitchings.

Yalow’s longtime collaborator at the VA Hospital, Solomon Berson, was both her competitor and her foil. Both were aggressive and pushed the other to do better, although their scientific skills were complementary—Berson the biochemist and Yalow the nuclear physicist were both key to the development of radioimmunoassay. In public Berson always took the lead, speaking on behalf of the team at conferences and with colleagues. Yalow, either out of genuine respect or mere necessity, went along with it; one of Yalow’s biographers noted: “at home, Yalow never conceded an argument, but in the lab, Berson was always right.” Regardless, the partnership worked, and in 1977 Yalow won the Nobel Prize for their mutual discovery. (Berson would have shared it with her, but he died five years before the Prize was awarded.)

Once they’d established their own careers, both women became mentors in their own right. Elion established a scholarship at Hunter College for women interested in graduate studies in chemistry or biochemistry. Yalow changed her own career path to help a talented up-and-coming scientist. “I stayed on at Hunter for an extra year because I had an outstanding student, Mildred Dresselhaus, whom I couldn’t abandon at that point in her career,” she told interviewer Susan Ambrose. “I wanted to teach her because she had so much potential.” Dresselhaus, now in her 80s, has been a professor of physics and electrical engineering at MIT since the 1960s. “Rosalyn's teaching style made you feel that the class was coming from someone who was personally involved in doing research,” she said. Through her connection with Yalow, Dresselhaus met many other scientific trailblazers, including Elion.

Today, more young, ambitious women have the advantage of female mentors working at at high levels—more than half of all biologists in 2008 were women, for example. The Obama administration has encouraged federal agencies to “increase mentorship of girls and women in STEM”; at least one of these agencies, the Department of Energy, features women in STEM on its website to “inspire others as they think about the future.”

But alliances with men who are well established in the field may still prove to be even more strategic, particularly in fields where female role models are harder to find. In the tech industry, for instance, women still struggle to score leadership positions, despite the presence of high-profile leaders like Sheryl Sandberg and Marissa Mayer. In such cases, “cross-gender mentoring may be the best way to go,” said Kandace Hinton, a professor of education at Indiana State University in Terre Haute. “If you can get men on board and supporting women, because men are already ingrained [in the field], those guys can move you forward.”

In almost all ways, today’s aspiring female scientists face better odds than Yalow and Elion encountered. Toys like Goldieblox get young girls interested in tinkering with engineering problems, not just playing make-believe. In high school, girls are earning more credits in math and science courses than their male peers—a trend that began in 1994 and has grown ever since. The number of degrees awarded to women in almost every scientific field has also steadily increased since 1991, most notably in the physical sciences.

Even so, many women start abandoning STEM majors early in college, according to research done by UCLA’s Jane Margolis. Although women enter college with the same high school STEM achievements as men, they are less likely to pursue a degree in a STEM field, often put off by the culture of male-dominated departments. In the introduction to their 2003 book, which centers on the computer sciences department at Carnegie Mellon University, Margolis and co-author Allan Fisher write: “By the time they finish college, most women studying computer science have faced a technical culture whose values often do not match their own and have encountered a variety of discouraging experiences with teachers, peers and curriculum. Many end up doubting their basic intelligence and their fitness to pursue computing.”

For this reason, stories like Yalow’s and Elion’s still offer much-needed inspiration. As Hinton of Indiana State University put it, discussing another female scientific trailblazer: “She made it, she had hard knocks, she had callouses that were never dissolved … Perhaps her story will resonate with someone else.”