The largest human cell is the female egg cell or ovum. The ovum is the reproductive cell or gamete produced by the female reproductive system. It is also known as the largest cell in the human body, measuring about 0.1 millimeters in diameter, which is visible to the naked eye.

The ovum is produced by the female body through a process called oogenesis, which begins during fetal development and continues until menopause. During this process, immature ova, called primary oocytes, undergo meiosis, which results in the formation of haploid secondary oocytes and polar bodies. The secondary oocyte is the mature ovum, which is released from the ovary during ovulation and travels through the fallopian tube where it may be fertilized by a sperm.

The large size of the ovum is due to the presence of yolk, a nutrient-rich substance that provides the developing embryo with the energy and nutrients required for growth until the placenta is fully formed. Unlike other cells in the human body, the ovum is not capable of replicating itself or undergoing cell division, which is why it is classified as a haploid cell.

In contrast, the male reproductive cell or sperm is the smallest cell in the human body, measuring only 50 micrometers in length. The sperm is produced in the testicles through a process called spermatogenesis and is released during ejaculation. The small size of the sperm allows it to move quickly through the female reproductive tract in search of the ovum.