We have non polar side chains, which are hydrophobic, and we also have polar side chains, which are hydrophilic. So it turns out if we take our polymer of amino acids, if we take the polypeptide and place it into an aqueous solution, the hydrophobic effect and hydrophobic interactions will take into effect. And what that means is all those amino acids that contain the nonpolar hydrophobic groups, for example, Valine, Alanine, Leucine, isolucine, methionine, Tryptophan, phenylalanine, and so forth, all these different non polar side chains will end up aggregating together in the core at the center of that protein. While all those amino acids that contain the polar side chains, for example Lysine or Arginine, Aspartate, and so forth, all these charged and polar amino acids will be found on the surface of that protein. So this is what we mean by the hydrophobic effect, essentially dictating the way that the tertiary structure is actually formed. So let's suppose, let's take a look at the following diagram.