Final answer:
Robert Hooke first coined the term "cell", but Matthias Schleiden and Theodor Schwann were the main contributors to the unified cell theory, stating that all living things consist of cells, which are the basic unit of life. Rudolf Virchow later added that all cells arise from pre-existing cells.
Step-by-step explanation:
The contributions to the cell theory can be attributed to several scientists over the course of history. Robert Hooke was the first to coin the term "cell" after observing cork tissue under a microscope. However, it was not until the 1800s that the cell theory began to take its modern form. Matthias Schleiden, a botanist, put forth the idea that plant tissues were made of cells. Theodor Schwann, a physiologist, made similar observations in animal tissues and realized the similarities between plant and animal cells. This lead to the proposal of the unified cell theory stating that all living things are composed of cells, which are the basic unit of life, and that new cells arise from existing cells. Later on, Rudolf Virchow contributed to the theory by proposing that all cells come from the division of pre-existing cells.