So the hydrocarbon portion of the adjacent hydrocarbon tails of these adjacent phospholipids. Now, when the fossil lipid tries to rotate, it actually has to physically rotate and move through that hydrocarbon core of the membrane. Hydrocarbon core of that membrane. And when this happens is we actually lose these stabilizing interactions here and these stabilizing interactions here, as shown in this particular case. So basically, the polar head does not actually want to interact and cannot interact in a stabilizing way with that hydrophobic core of the membrane. And likewise, the non polar tail portion of the fossil lipid also cannot and does not want to interact with the water molecules of the aqueous environment.