Name the scientists who proposed cell theory. Who gave the idea that the cells arise from pre-existing cells.

Explanation

### Step-by-Step Solution:

1. **Understanding Cell Theory**: The cell theory is a fundamental concept in biology that describes the properties of cells, which are the basic unit of life.

2. **Identifying the Scientists**: The scientists who proposed the original cell theory are:
- **Matthias Schleiden** (1838) - He stated that all plants are made of cells.
- **Theodor Schwann** (1839) - He extended this idea to animals, stating that all animals are also made of cells.

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