Answer the following question given this paragraph: 

hydrophilic heads are directed outward, in contact with the water. Each micelle may contain thousands of lipid molecules. Polar lipids may also form a monolayer, a layer one molecule thick on the surface of the water. The polar heads face into water, and the nonpolar tails stick up into the air. Bilayers are double layers of lipids arranged so that the hydrophobic tails are sandwiched between an inner surface and an outer surface consisting of hydrophilic heads. The hydrophilic heads are in contact with water on either side of the bilayer, whereas the tails, sequestered inside the bilayer, are prevented from having contact with the water. Bilayers like this make up every cell membrane (Figure 17.6 "Schematic Diagram of a Cell Membrane"). Figure 17.5 Spontaneously Formed Polar Lipid Structures in Water: Monolayer, Micelle, and Bilayer.


Q: When something is described as "hydrophilic", you can determine something about how it interacts with what?


A:
water