**Core Concept**
Karyotyping is the process of analyzing the number and structure of chromosomes in a cell. There are different techniques used to visualize chromosomes, including light microscopy, fluorescence microscopy, and banding techniques.

**Why the Correct Answer is Right**
Giemsa staining is a type of banding technique that is performed under light microscopy. This staining method involves mixing acridine orange with Giemsa stain, which binds to the chromosomal DNA and produces a banding pattern that allows for the identification of specific chromosomes. The resulting karyotype can be analyzed for abnormalities such as deletions, duplications, and translocations.

**Why Each Wrong Option is Incorrect**
* **Option A:** Chromosome painting is a technique that uses fluorescent probes to visualize specific chromosomes under fluorescence microscopy, making it an incorrect choice.
* **Option B:** FISH (Fluorescence In Situ Hybridization) is a molecular cytogenetic technique that uses fluorescent probes to detect and locate specific DNA sequences on chromosomes, also performed under fluorescence microscopy.
* **Option D:** Spectral karyotyping is a technique that uses multiple fluorescent dyes to visualize chromosomes under fluorescence microscopy, making it an incorrect choice.

**Clinical Pearl / High-Yield Fact**
Giemsa staining is a widely used technique for karyotyping, but it has limitations, including the ability to detect only a few hundred bands per chromosome. Newer techniques such as spectral karyotyping and FISH offer higher resolution and can detect more subtle chromosomal abnormalities.

**Correct Answer: C. Giemsa staining**