The cell theory was established by ........

Explanation

**Step-by-Step Text Solution:**

1. **Identify the Founders of Cell Theory**: The cell theory was established by two scientists, Matthias Schleiden and Theodor Schwann. They proposed the foundational ideas about cells in the early 19th century.

2. **Year of Establishment**: The cell theory was formulated in the year 1830.

3. **Revision of the Theory**: The cell theory was later revised by Rudolf Virchow, who contributed to the understanding of cell division.

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