Final answer:
William Perkin's contribution to Cell Biology was the invention of the first synthetic dye, mauveine, which played a key role in the development of staining techniques.
Step-by-step explanation:
William Perkin's contribution to Cell Biology was the invention of the first synthetic dye, called mauveine or more commonly known as mauve. Perkin accidentally discovered this dye while attempting to synthesize quinine, a treatment for malaria. This invention played a key role in the development of staining techniques, which allowed scientists to see different components inside cells under a microscope.