So I was making a cappuccino and I started to wonder - how does the foam form? I have no problem with the foam itself, milk contains a lot of surfactants that can stabilize the bubbles. But what is inside bubbles? My espresso machine makes steam, that is bubbled through the milk, creating foam. What I don't get is why the steam doesn't condense and why the bubbles don't collapse after the foam is cooled down?