In addition to friendship and romance, the characters' careers are also a huge area of focus on The Big Bang Theory. The Big Bang Theory follows four scientists, two of whom are roommates, as they navigate their lives in and out of their work at the university. Many of their more humorous interactions is the result of their interactions with people outside of the academic world, like Penny, but their careers still play a huge role in the series.

After all, a majority of Sheldon's quirks are related to his fascination and dedication to the sciences. With everyone working in the sciences (aside from Penny when she was a struggling actress), work isn't just the topic of conversation at dinner; it's their livelihood. The gang has fun at work because they're passionate about what they do. But what exactly do the characters on The Big Bang Theory do? Each character works in a different field, but that doesn't keep them from sharing their experiences, problems, and accomplishments with each other.

Raj

Astrophysicist

Raj's (Kunal Nayyar) work doesn't often get the spotlight since more attention is paid to Sheldon, and even Howard's, career goals. His work, however, isn't so far removed from Sheldon's. After attending the University of Cambridge, Raj got his PhD in astrophysics and became an astrophysicist at Caltech.

As much as Sheldon acts like he's smarter than everyone else and doesn't need to work in teams.

While at Caltech, Raj was part of the squad that created a data-collecting space probe on Pluto and ended up winning multiple awards for his research. Later, he teamed up with Sheldon to work on string theory and dark matter. As much as Sheldon acts like he's smarter than everyone else and doesn't need to work in teams, Raj's input was invaluable and helped Sheldon tremendously. By the end of the series, Raj was still working at Caltech but got a job at the Griffith Observatory as a hobby.

Sheldon

Theoretical Physicist

One of the brightest characters on The Big Bang Theory is Sheldon Cooper (Jim Parsons). He skipped several grades of school as a child and went to university very early. At the tender age of 16, Sheldon received his PhD, but he also has his Bachelor of Science, Master of Science, Master of Arts, and his Doctor of Science. With an IQ of 187, Sheldon works at Caltech as a theoretical physicist focusing on string theory.

He later changes his focus to dark matter when he hits a dead end with his study of string theory. However, Sheldon never completely lets string theory go. With Amy's help, they put their energy towards string theory's super-asymmetry and won a Nobel Prize for their accomplishments together. By the end of the series, Sheldon is still profoundly happy at Caltech working in the Physics Department.

Leonard

Experimental Physicist

After attending Princeton and getting his PhD in physics, Leonard (Johnny Galecki) became an experimental physicist at Caltech, which is where he met his three best friends. As an experimental physicist, Leonard actually gets to see how things work in the lab instead of listing mathematical equations on a board like so many of his colleagues.

His work was published in a few prominent journals, and he was recognized for his contributions to science. This resulted in his career when he began working for the U.S. government with Howard and Sheldon. He even got to work on the North Sea with a team organized by the legendary Stephen Hawking. At the end of the series, Leonard was at a standstill professionally but still did amazing work that was recognized by both Sheldon and President Siebert.

Howard

Engineer & Former Astronaut

Although Howard (Simon Helberg) gets little respect from Sheldon, he really is a fantastic engineer who should be praised for his work. Howard attended MIT where he got his Master's Degree in Engineering, with a focus on aerospace. He had the ability to control the Mars Rover and helped design a satellite that circled Jupiter. Those are huge career achievements for someone in his field already.

He later invented a Quantum Guidance System for the U.S. Air Force with a theory created by Leonard and Sheldon.

Due to his experience with space, Howard had the opportunity to work with NASA and go to the International Space Station. It was one of the most rewarding experiences of his career, though it was hard work for him to get to that point since he had to be vetted by government agents for his big projects. He later invented a Quantum Guidance System for the U.S. Air Force with a theory created by Leonard and Sheldon.

Penny

Actress, Waitress, Pharmaceutical Sales Rep.

When Penny (Kaley Cuoco) first started the series, she was newer to Los Angeles and was trying to become an actress. In between auditions, she got a waitressing job at The Cheesecake Factory to pay her bills. She needed a steady job when she wasn't getting callbacks at auditions, even if it wasn't something she loved. Sadly, Penny realized her acting career wasn't going anywhere, so she got a job as a pharmaceutical sales rep at Bernadette's company.

Penny didn't love "flirting with doctors for money" but she was making more money than she ever had before. She even doubled Leonard's salary! When Penny found her footing in pharmaceuticals, Bernadette recruited her to be the head of her sales team. She even dabbled in public relations as well. Penny was able to use some of the skills she required in waitressing and acting to be an excellent sales person.

Bernadette

Microbiologist

When Bernadette (Melissa Rauch) was first introduced, she was a fellow waitress at The Cheesecake Factory who was getting her degree in microbiology. She and Penny worked together while Bernadette worked toward getting her doctorate. After she and Howard became serious, she began working for a company that paid for her to get her PhD, so she no longer needed the job as a waitress, which likely helped her have better focus on her work.

Later in the series, it's noted that Bernadette is the head of her department at a pharmaceutical company called ZanGen. Bernadette is very good at her job because she rises through the ranks very quickly. When her company hires Penny, the series shows how powerful Bernadette is in her role and makes it clear that she makes a "butt load" of money.

Amy

Neurobiologist

Amy (Mayim Bialik) is a Harvard graduate who has her PhD in neurobiology. Bialik was actually well-prepared for the role of Amy since she has her degree in the same field after taking a break from the world of acting to pursue her education.

While she didn't work at Caltech with the guys, she did get transferred there for a few weeks to do a study.

Not much is said about Amy's day-to-day life in the lab, but she has talked about her research with capuchin monkies. While she didn't work at Caltech with the guys, she did get transferred there for a few weeks to do a study. She has also mentioned doing work at UCLA's lab as well, which could be where she worked full-time as a researcher. By the end of the series, Amy's knowledge of neuroscience helped Sheldon with his work in physics, which ultimately won the two of them a Nobel Prize.

Stuart

Business Owner

Stuart (Kevin Sussman) isn't one of the main scientists in the series, but he is an important part of the show. Sussman guest starred in early episodes and became a recurring character as Stuart's business is a main location of the series. His comic book store is frequented by the main characters, and he has a tentative friendship with the group.

As the owner of the comic book store, Stuart had a hard time getting his business off the ground but it finally paid off later in the series. It's not known if he had a real passion for owning a store, but his degree from Rhode Island School of Design proved that he enjoyed comic book illustrations. It was great for fans to see his business finally make a profit by the end of The Big Bang Theory.