The middle ear is composed of the tympanic chamber, sinus, mastoid process, and eustachian tube, so anatomically speaking, the mastoid process is part of the middle ear, which begins to develop at age 2 and is basically completed at age 6. The mastoid process is composed of interconnected air-containing cavities of different sizes, in the shape of a small honeycomb. These mastoid cavities can be divided into several groups, which are located at the mastoid tip, the lid of the sky, around the sigmoid sinus, around the labyrinth, and at the tip of the rock, etc. The surface is covered by cilia-free mucosal epithelium, which is connected to the middle ear mucosa. Therefore, otitis media often includes mastoiditis, where you have me and I have you. This is the reason why mastoid surgery is often included in otitis media surgery.