Nucleus was first described by:-

Answer

**Step-by-Step Solution:**

1. **Identify the Subject of the Question**: The question asks about the first person to describe the nucleus, which is a vital cell organelle.

2. **Recall Historical Context**: The nucleus was first described in the context of cell biology. Understanding the timeline of discoveries in cell biology is essential.

3. **Name the Scientist**: The scientist who first described the nucleus is Robert Brown.

4. **Provide the Year of Discovery**: Robert Brown made this description in the year 1831.

5. **Explain the Significance**: The nucleus is a double membrane structure and is essential for cellular functions. It contains chromatin fibers and nucleoli, which play crucial roles in genetics and cell regulation.

6. **Mention Subsequent Discoveries**: After its initial description, the nucleus was later stained with a basic dye, which helped in identifying its components like chromatin.

**Final Answer**: The nucleus was first described by Robert Brown in the year 1831.

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