State briefly the three major points of the cell theory as proposed by Schwann and Schleiden and modified by Virchow.

The three major points of the cell theory as proposed by Schwann and Schleiden and modified by Virchow are:

1. All living organisms are composed of one or more cells. This point was proposed by both Schwann and Schleiden, stating that the cell is the basic unit of life.

2. The cell is the basic unit of structure and organization in organisms. This point further emphasizes the first point by stating that cells provide structure for the body, take in nutrients from food and carry out important functions.

3. Cells arise from pre-existing cells. This point was added by Virchow, modifying the original cell theory by proposing that new cells are formed from the division of existing cells. This concept refuted the previous idea of spontaneous generation.