What part of our ear responsible for making them pop?

The part of the ear responsible for the sensation of popping is the Eustachian tube. This tube connects the middle ear to the back of the throat and helps equalize pressure between the middle ear and the external environment. When there's a change in altitude or pressure, such as during takeoff or landing in an airplane, the Eustachian tube opens to allow air to enter or escape, which causes the popping sensation. This is a normal response to balance the pressure in the ear.