The correct answer is option 2: Robert Hooke. Robert Hooke was an English scientist who first discovered cells in 1665. He used a microscope to examine a thin slice of cork and observed small box-like structures, which he called "cells" due to their resemblance to the cells of a monastery. Although Hooke`s understanding of cells was limited compared to our current knowledge, his discovery laid the foundation for the study of cell biology.

Option 1: Robert Brown is not the correct answer. Robert Brown was a botanist who discovered and described the cell nucleus in plant cells in 1831. However, the discovery of the cell itself was made by Robert Hooke.

Option 3: Leeuwenhoek is not the correct answer. Although Leeuwenhoek is known as the "Father of Microbiology" and made significant contributions to the field, he did not discover cells. He is known for his observations of microorganisms using a microscope.

Option 4: Rudolf Virchow is not the correct answer. Rudolf Virchow was a German physician and is best known for his contributions to pathology. He proposed the theory of biogenesis, which states that cells arise from pre-existing cells. While Virchow`s theory was