**Core Concept**
Pemphigus vulgaris is an autoimmune skin disease characterized by the formation of blisters due to the breakdown of skin cell adhesion. The Fish Net pattern is a histopathological feature seen in pemphigus vulgaris, where the intercellular connections between skin cells are disrupted, leading to a characteristic "fish net" appearance under the microscope.

**Why the Correct Answer is Right**
The Fish Net pattern is seen in direct immunofluorescence (DIF) tests, where antibodies against desmoglein 3 proteins are deposited in the intercellular spaces of skin cells, causing the characteristic disruption of cell adhesion and formation of blisters. This is a hallmark feature of pemphigus vulgaris and can be used for diagnostic purposes.

**Why Each Wrong Option is Incorrect**
**Option A:** - Indirect immunofluorescence (IIF) tests are used to detect antibodies against skin proteins, but they do not show the Fish Net pattern.
**Option B:** - Electron microscopy can show the ultrastructural changes in skin cells, but it is not the primary method used to diagnose pemphigus vulgaris.
**Option C:** - Immunoperoxidase staining is a technique used to detect antigens, but it is not typically used to visualize the Fish Net pattern in pemphigus vulgaris.

**Clinical Pearl / High-Yield Fact**
The Fish Net pattern is a highly specific feature of pemphigus vulgaris, and its presence on DIF tests can be used to confirm the diagnosis. This can help differentiate pemphigus vulgaris from other autoimmune skin diseases.

**Correct Answer:** C. Immunofluorescence.