Cystic dark areas of the ovary can be classified as either physiological or pathological. If the ovarian cystic dark areas are physiological, they are mostly seen in the development of follicles or corpus luteum in the ovary. If the cystic dark areas of the ovaries are pathological, they may be cystic changes of ovarian tumors, also known as ovarian cysts. Physiological cystic dark areas in the ovary mainly refer to the development of follicles in the ovary. Every month, on the 5th-7th day of menstruation, a group of follicles will develop in the ovary, but only one follicle will become the dominant follicle and grow the fastest. As the follicle grows, a cystic dark area can be seen in the ovary under ultrasound, but when the follicle grows to 18-22mm, it becomes a mature follicle and can expel the egg. After the mature follicle expels the egg, the remaining follicular structures are wrapped up in the ovary and the corpus luteum will form, which continues to increase in size. With the enlargement of the corpus luteum, it is possible to see cystic dark areas within the ovary, which at this time is the presence of a corpus luteum cyst. If the sperm and egg do not unite and conception does not occur, after the corpus luteum develops to a certain extent, on the 9th-10th day after ovulation, the corpus luteum will rapidly shrink, so the luteal cysts will disappear when the ultrasound is repeated 2-3 months later.