Microorganisms play a central role in driving Earth’s biogeochemical cycles, yet they are often invisible and challenging to study. This course focuses on microbial biogeochemistry in the ocean, while emphasizing that many of the same processes operate in other ecosystems (e.g., soils and wetlands), engineered systems (e.g., wastewater treatment plants) and hosts (e.g., human). I will cover fundamental microbial concepts, including microbial ecology, evolutionary history, microbial metabolisms, and how microbial metabolisms are linked to nutrient cycling. Beyond basic concepts and principles, this course emphasizes how this knowledge was obtained. Students will be introduced to key approaches used to study microbes in global biogeochemical cycles, including both experimental and computational methods such as stable isotope techniques, metagenomics, theoretical frameworks, and modeling. The course develops essential scientific skills: reading and critically evaluating research papers, presenting scientific findings to peers, and communicating science to broader audiences. Through hands-on activities, students will practice translating complex microbial biogeochemical research into clear and engaging outreach articles, with the opportunity to develop a piece suitable for publication.