The structure of the ear is divided into three parts: the outer ear, the middle ear, and the inner ear. The outer ear receives sound from the outside world and will cause the eardrum to vibrate along the ear canal. The vibration of the middle ear tympanic membrane causes three small bones – the concha, stapes and drusen – to vibrate in the upper phase and transmit the sound to the inner ear. The inner ear generates nerve impulses, which are converted into neural energy along the auditory nerve, and from there sound information is transmitted to the brain. The human ear has the function of producing the sense of hearing and balance. The normal human ear can distinguish approximately 400,000 different sounds, some of which are so small that they can only move the eardrum one tenth of the diameter of a hydrogen molecule. So how do we hear sounds? When a sound is made, the surrounding air molecules start a series of vibrations, which are sound waves that travel outward from the sound source. When the sound reaches the outer ear, it is transmitted into the external auditory canal and reaches the tympanic membrane through the sound collecting action of the auricle. The tympanic membrane is the dividing line between the outer and middle ears and is as thin as paper, but very strong. When sound waves hit the eardrum, they cause it to vibrate. Behind the eardrum, in the middle ear cavity, are three interconnected auditory ossicles. Each one is the size of a grain of rice, making them the smallest bones in the human body. They get their name from their shape. Next to the tympanic membrane is the mallet bone (like a mallet), followed by the anvil bone (like an anvil), and finally the stirrup bone (like a stirrup). When sound waves vibrate the tympanic membrane, the ossicles also vibrate, and the three ossicles actually form a lever system that amplifies sound and transmits it to the inner ear; the last of the three ossicles, the stapes, is attached to a tiny membrane called the oval window. The oval window is the gateway to the inner ear, which contains the cochlea, an organ dedicated to hearing. When the stapes vibrates, the oval window vibrates with it. On the other side of the oval window is the fluid-filled cochlear duct. When the oval window is vibrated, the fluid also begins to flow. The cochlea contains thousands of hair cells with tiny cilia at their apex. As the fluid flows, the cilia of these cells are impacted and undergo a series of bioelectrical changes, the hair cells convert the sound signal into a bioelectrical signal that is transmitted to the brain via the auditory nerve. The brain then processes and integrates the information sent to it to produce the sense of hearing. Sound waves are transmitted through the outer and middle ears to the inner ear and then through the auditory nerve fibers to the brainstem and higher auditory centers. In addition, the inner ear contains a very important organ, the semicircular canal. The semicircular canal is composed of three small rings that are perpendicular to each other and specialize in the sense of balance in the three-dimensional space of the head. When the semicircular canal is faulty, symptoms of vertigo may occur. Hearing is a necessary communication channel for human social life. However, most importantly, hearing allows us to perceive our environment and create a sense of security and involvement. Hearing is important for health. Therefore, please take care of your ears.