Who observed bacteria for the first time?

Explanation

**Step-by-Step Solution:**

1. **Understanding Bacteria**: Bacteria are classified as prokaryotes, which means they have a simple cell structure without a nucleus. They are unicellular organisms, meaning they consist of a single cell.

2. **Historical Context**: The question asks about the first observation of bacteria. This relates to the history of microbiology.

3. **Identifying the Scientist**: The first person to observe bacteria was Antony von Leeuwenhoek. He made significant contributions to the field of microbiology.

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