Oocytes are the female reproductive cells, also known as egg cells, that are essential for sexual reproduction. They are produced in the ovaries and undergo a process called oogenesis, which involves several stages of development. Each woman is born with a finite number of oocytes, which decrease in quantity and quality as she ages. During the menstrual cycle, a few oocytes begin to mature, but typically only one is released during ovulation. If an oocyte is fertilized by a sperm cell, it can develop into an embryo, leading to pregnancy. The health and viability of oocytes are crucial for fertility and reproductive success.