Introduction - This script shows the structure of the phospholipids in a bilayer. Scroll down until the text corresponding to the view is visible.(Based on a molecular model of the bilayer generated by molecular dynamic calculations, Heller et al.  J. Phys. Chem. 97 8343 (1993)).

Here is the arrangement of phospholipids in a bilayer. Notice the close packing of the fatty acyl chains.

Here is a view from the top. Note the close packing of the polar head groups.

  The bilayer can exist in a highly ordered crystalline state, as shown here.

Or, the bilayer can exist in a more disordered fluid state, as shown here. The fluid state is more representative of the state of the phospholipids in a natural membrane.