Scientific theory is a well-tested explanation for a broad range of observations. They are accepted as truth, but can be revised with further observations, discovery and testing. Scientists once believed life spontaneously arose from nonliving things. The three parts of the cell theory as we know it today came from the work of multiple scientists over many years. Which of the following scientists contributed to the cell theory? A) Robert Hooke

B) Charles Darwin

C) Gregor Mendel

D) Isaac Newton