And in the diagram these arrows are basically our backbone. Now what they were able to show is that the backbone is found on the outside portion, on the exterior portion of that DNA molecule and that's because these phosphate groups found on a backbone contain negative charges and they are stabilized by the aqueous environment that contains polar water molecules. And we'll examine that in much more detail in the next several electros. Now if the backbone is found on the exterior, then the interior, the inside of that double helix essentially contains the nitrogenous bases. So if we examine on the inside portion of our molecule, we have these nitrogenous bases, which are relatively non polar, while on the outside we have the actual strand, we have the backbone that contains the sugar and phosphate groups, and these are found on the outside. Point number three.