What scientific field does Bernadette study in graduate school?

Bernadette Rostenkowski-Wolowitz studies microbiology in graduate school.

When Bernadette is introduced in The Big Bang Theory, she works at The Cheesecake Factory with Penny while paying her way through graduate school. Her chosen field is microbiology, the study of microorganisms such as bacteria, fungi, and other microscopic life. The subject gives her a scientific identity distinct from Amy’s neurobiology and the men’s physics-heavy careers.

Bernadette eventually earns her doctorate and moves into pharmaceutical research. Her professional work involves developing medicines, making microbiology a useful foundation for a career in biotechnology and drug development. The show later presents her as a highly successful scientist with a demanding corporate job.

Viewers sometimes remember Bernadette simply as a biologist, which is broadly reasonable, but microbiology is the more precise answer used by the series. Her waitress job is also easy to mistake for her main occupation; it was a way to support herself while completing advanced scientific study.