Hysteroscopy is a technique that is very widely used in medicine. This technique allows the examination of diseases in the uterine cavity and also the treatment of lesions in the uterine cavity. Many people are unaware of what hysteroscopy does, so now it is time to explain what diseases are investigated by hysteroscopy. A hysteroscope is an endoscope made with a fiber optic light source. Hysteroscopy, an invasive test, is one of the simplest gynecologic procedures. It can reach inside the uterine cavity and with the help of the hysteroscope can probe the morphology, size, and position of the opening of the fallopian tubes, the size, scope, appearance, location and distribution of the lesion located in the uterine cavity, and also perform an indicative tissue biopsy of the lesion. In clinical practice, hysteroscopy is usually used for the examination of gynecological diseases. For example, some patients with long-term infertility or tubal reopening, or women with symptoms such as amenorrhea or pain during intercourse, can use hysteroscopy to understand the internal condition of the uterus and check whether these symptoms occur due to uterine cavity lesions; for known endometrial lesions such as endometrial polyps and submucosal fibroids, the specific location and shape of the polyps can be found through hysteroscopy. Tissue biopsies can also be obtained through hysteroscopy and further sent for pathological examination to clarify the nature of the lesions. However, the disadvantage of hysteroscopy is that it cannot be used for simultaneous treatment. If hysteroscopy is needed for surgical excision, it needs to be replaced by a therapeutic mirror with operating instruments, which is relatively thicker than the examination mirror and requires dilatation of the cervical canal before it can be placed into the uterine cavity for the purpose of surgical excision.