## Core Concept
The process of **meiosis** in the testes is crucial for sexual reproduction as it leads to the production of genetically diverse gametes. **Spermatogenesis**, the development of sperm cells, involves both mitosis and meiosis. The cells that undergo meiosis are a key part of this process.

## Why the Correct Answer is Right
The correct answer involves **spermatocytes**. Specifically, **primary spermatocytes** undergo **meiosis I** to produce **secondary spermatocytes**, which then undergo **meiosis II** to produce **spermatids**. These spermatids eventually mature into spermatozoa (sperm cells). The primary spermatocytes are diploid cells (2n) that undergo meiosis I to become haploid (n) secondary spermatocytes. This meiotic division is essential for reducing the chromosome number by half, ensuring that when fertilization occurs, the resulting zygote has the correct diploid number of chromosomes.

## Why Each Wrong Option is Incorrect
- **Option A:** Leydig cells, also known as **interstitial cells of Leydig**, are involved in the production of **testosterone**, which is crucial for spermatogenesis and the development of male secondary sexual characteristics. However, they do not undergo meiosis.
- **Option B:** Sertoli cells, or **nurse cells**, play a supportive role in the development of sperm cells within the seminiferous tubules of the testes. They do not undergo meiosis.
- **Option D:** Spermatogonia are the diploid cells from which sperm cells originate. They undergo **mitosis** to proliferate and some of them will eventually undergo **meiosis** to become sperm cells, but they themselves do not undergo meiosis.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **spermatogenesis** is a complex process involving both **mitosis** (for spermatogonia) and **meiosis** (for spermatocytes). Disruptions in this process can lead to male infertility.

## Correct Answer: C. Spermatocytes.