In which substance cells were first observed ?

Options

A. Cork
B. Skin
C. Onion
D. Leaf

Explanation

**Step-by-Step Solution:**

1. **Identify the Scientist**: The first step is to recognize the scientist who made the observation of cells. The scientist is Robert Hooke.

2. **Year of Observation**: Note the year when this observation took place, which is 1665.

3. **Substance Used**: Understand the substance that was used for the observation. Robert Hooke used cork, which is a part of the bark of a tree.

4. **Description of Cork**: Recognize that cork is a dead, brown-colored structure that surrounds the stem of a plant.

5. **Microscope Observation**: Hooke examined the cork under a microscope, where he observed the structure of the cork.

6. **Shape of Cells**: He noted that the cells appeared hexagonal (six-sided) and looked empty inside.

7. **Naming of Cells**: Hooke referred to these structures as "cells," which is derived from the Greek word for "compartment."

8. **Conclusion**: Therefore, the substance in which cells were first observed is cork.

**Final Answer**: Cells were first observed in cork.

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