Now, they resemble balloons in that we actually have to apply a certain pressure to inflate them. But when we release that pressure, when the pressure is removed, the elasticity of our balloons causes them to actually deflate and return back to their original shape. So let's take a look at the following microscopic sections. So, this is our bronchiol. And the bronchiol eventually connects to this space. And around this space, we have many of these alveoli.