1. Biologist: Studies living organisms and their processes. This can encompass a vast range of specialties like zoology, botany, genetics, microbiology, and more.

2. Physicist: Explores the fundamental laws of nature, including matter, energy, space, and time. They might focus on areas like astrophysics, quantum mechanics, or nuclear physics.

3. Chemist: Investigates the composition, structure, properties, and reactions of matter. This field includes organic chemistry, inorganic chemistry, analytical chemistry, and many more.

4. Computer Scientist: Develops and studies algorithms, computational systems, and programming languages. They can work on everything from artificial intelligence to cybersecurity.