Louis Agassiz was a Swiss-American naturalist and geologist, born on May 28, 1807. He is best known for his contributions to the study of glaciers and the theory of ice ages. Agassiz emphasized the importance of direct observation in scientific research and was a strong advocate for the study of fossils and marine biology. Agassiz also played a significant role in the development of ichthyology, the study of fish, and he published several influential works on the subject. He founded the Museum of Comparative Zoology at Harvard University, which became a major center for research and education in the natural sciences.