OK, Soufflés poof up like a hot air balloon! Meringue does not but holds it's air. So, I am going to go out on a limb. pros and more experienced folks, please confirm or correct me, here. I am going to postulate that egg whites can gather air and hold it but whites are not very elastic. hence, you have this lovely crispiness in meringues and light, airiness but the meringue holds it's shape. The egg yolks provide elasticity. which is why soufflés grow instead of being the same size as they enter the oven. however, the yolks don't have strength, which is why soufflés fall. Angle food cake inflates using the flour for elasticity and creates more air with the leavening as well as moisture. they, too can fall if handled wrong but, handled correctly and cooled upside down, one cool, the matrix between the egg whites and flour (now cake with light gluten) is strong enough to hold the cavities open. So, my thought is that whites can hold the air but whites are not very elastic. you can find that in the yolks but you buy your elasticity with time, the time it takes to go from the oven to the table. Am I understanding the chemistry of baking eggs correctly, here?