Name the innermost extra-embryonic membrane.

Explanation

**Step-by-Step Solution:**

1. **Understanding Extraembryonic Membranes**: There are four types of extraembryonic membranes that support the developing embryo. These include the chorion, amnion, allantois, and yolk sac.

2. **Identifying the Layers**:
- The **chorion** is the outermost layer and is attached to the placenta, providing protection.
- The **amnion** is the next layer, located inside the chorion, and is directly attached to the embryo.

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