A biologist is studying a structure that is made up of two layers of phospholipids. What is she most likely studying?

Phospholipid Bilayer

Explanation:

The cellular phospholipid bilayer has 2 layers of phospholipids (obviously), but keep in mind that the heads of said phospholipids are hydrophillic (loving water) and the tails are hydrophobic (hating water). This makes the 2 layers line up with heads facing away from each other and tails facing each other. This is so the bilayer can exist in the aqueous enviorment outside the cell as a barrier and inside the aqueous enviorment of the cell to transport materials in and out of the cell.