Final answer:
The Cell Theory, fundamental to biology, asserts that all living organisms are made of cells, the cell is the basic unit of life, and all cells originate from existing cells, with key contributions from scientists such as Schleiden, Schwann, and Virchow.
Step-by-step explanation:
Cell Theory and Its Founders
The Cell Theory is a cornerstone of modern biology, positing that the cell is the fundamental unit of life. Three main tenets define this theory: all living organisms are composed of cells, the cell is the basic unit of life, and all cells come from pre-existing cells. Initially, in the 17th century, Robert Hooke discovered empty chambers in cork slices which he termed 'cells'.
Later, groundbreaking work by scientists Matthias Jakob Schleiden and Theodor Schwann in 1839 identified cells as the structural and functional units of plants and animals, respectively.
This idea was further advanced by Rudolf Virchow and Robert Remak in the 1850s, who provided evidence that cells arise from other cells, although controversy exists over who should be credited for this discovery due to the parallel nature of their research.