**Core Concept**
Spermatogenesis is a complex process of sperm cell development that occurs in the male reproductive system. It involves multiple stages, including spermatocytogenesis, meiosis, and spermiogenesis, ultimately resulting in the formation of mature spermatozoa.

**Why the Correct Answer is Right**
The last step of spermatogenesis is spermiogenesis, which is the process of sperm cell maturation. During this stage, the round spermatids undergo significant changes to become elongated spermatozoa with distinct head, neck, and tail structures. This process involves the formation of the acrosome, the development of the flagellum, and the condensation of chromatin. The epididymis is responsible for the final maturation of spermatozoa after they are released from the testes.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because spermatocytogenesis is the first step of spermatogenesis, where primitive germ cells (spermatogonia) undergo mitotic divisions to produce more spermatogonia and pre-leptotene spermatocytes.

**Option B:** This is incorrect because meiosis is a two-stage process (meiosis I and meiosis II) that occurs in the seminiferous tubules of the testes, but it is not the last step of spermatogenesis.

**Option C:** This is incorrect because the epididymis is involved in the final maturation of spermatozoa but is not the location of the last step of spermatogenesis.

**Clinical Pearl / High-Yield Fact**
Spermiogenesis is a highly regulated process, and any disruptions can lead to infertility or abnormal sperm morphology. Understanding the different stages of spermatogenesis is crucial for diagnosing and managing male infertility.

**Correct Answer:** D