What is the nature of cell walls in diatoms?

Explanation

**Step-by-Step Solution:**

1. **Understanding Diatoms**: Diatoms are a type of microalgae that are known for their unique cell structure.

2. **Composition of Cell Walls**: The cell walls of diatoms are primarily composed of silica (SiO2). This silica gives the cell walls their characteristic hardness and durability.

3. **Structure of Cell Walls**: The silica cell walls of diatoms are structured in a unique way, forming overlapping shells. These shells fit together like a soapbox, providing protection and structural integrity.

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