**Core Concept**
The Kayser-Fleischer ring is a pathognomonic sign of Wilson's disease, an inherited disorder of copper metabolism. The cornea plays a crucial role in the deposition of copper, which accumulates in the Descemet's membrane due to impaired biliary excretion and subsequent systemic copper overload.

**Why the Correct Answer is Right**
In Wilson's disease, the accumulation of copper in the cornea leads to the formation of a Kayser-Fleischer ring. This occurs due to the deposition of copper in the Descemet's membrane, a thin, basement membrane-like structure that separates the corneal stroma from the corneal endothelium. The Descemet's membrane is composed of type IV collagen and laminin, which provide a suitable environment for copper deposition. The corneal endothelium, responsible for maintaining corneal hydration, is not directly involved in copper deposition.

**Why Each Wrong Option is Incorrect**
**Option A:** Bowman's layer is a dense, acellular layer of the cornea, composed of tightly packed collagen fibers. It is not a site for copper deposition in Wilson's disease.
**Option B:** The corneal stroma is the thickest layer of the cornea, comprising about 90% of its thickness. It is composed of highly organized collagen fibers, but is not the primary site for copper deposition in Wilson's disease.
**Option D:** The corneal endothelium is a monolayer of cells lining the posterior surface of the cornea, responsible for maintaining corneal hydration. It is not directly involved in copper deposition or the formation of a Kayser-Fleischer ring.

**Clinical Pearl / High-Yield Fact**
The Kayser-Fleischer ring is a characteristic feature of Wilson's disease, but it can also be seen in other conditions, such as primary biliary cirrhosis and chronic copper exposure. A Kayser-Fleischer ring is a key diagnostic feature that can guide further investigations and management of these conditions.

✓ Correct Answer: C. Descemet's membrane