Final answer:
Robert Hooke, an English natural philosopher, first described cells in 1665 after observing cork tissues under a microscope, leading to crucial developments in cell theory.
Step-by-step explanation:
The natural philosopher who studied cork cells under a compound microscope in 1655 was Robert Hooke. In 1665, he published a seminal work called Micrographia, where he coined the term "cell" to describe the box-like structures he observed within cork tissue. Hooke's observations were a critical milestone in the scientific field, leading to the development of cell theory, which is foundational to our understanding of biological life. Illustrations from Micrographia depict cork cells as viewed under Hooke's microscope, resembling a "Honey-comb." This honeycomb structure is what prompted him to use the term cells, and these drawings are considered among the earliest recorded observations of cellular structure. Advances in microscopy since Hooke's time, such as improved lenses, microscope construction, and staining techniques, have vastly expanded our knowledge of cell biology.