So remember, what the hydrophobic effect tells us is if we take non polar molecules, hydrophobic molecules, and place them into a solution where water is that dominant molecule, because water is a polar molecule, what will happen is we'll find that those non polar molecules will basically aggregate together to form larger systems, larger chunks of nonpolar molecules. And that's because that system that is formed is thermodynamically stable. Now, what does that have to do with the folding of the proteins and the formation of the tertiary structure? So remember that proteins are polypeptides, consist of 20 different types of amino acids. And these amino acids differ from one another based on their side chain group. So we have different types of side chains.