Rudolf Virchow was a German pathologist and statesman who pioneered the modern concept of pathological processes by his application of the cell theory to explain the effects of disease in the organs and tissues of the body. He made several contributions to the study of cells, including:

• Cellular Pathology: Virchow helped to establish the concept of cellular pathology, which states that all diseases are caused by changes in normal cells. He argued that life was merely the sum of the processes of cellular activities.

• Omnis Cellula e Cellula: In 1855, Virchow published his famous aphorism "omnis cellula e cellula," which became a part of the foundation for cell theory. This theory states that new cells arise from pre-existing cells in both diseased and healthy tissue.

• Cancer: Virchow was the first to correctly link the origin of cancers from otherwise normal cells, believing that cancer is caused by severe irritation.

Therefore, Rudolf Virchows contributions to the study of cells include the concept of cellular pathology, the aphorism "omnis cellula e cellula," and the link between cancer and normal cells.