When a nitrogen (or other atom with unshared electrons) is adjacent to a double bond, it uses sp2 hybridization with the electron pair in a p orbital that is conjugated with the double bond. Thus, the N (blue) of pyrrole is sp2 hybridized. The electrons (red) on this N are in a p orbital that is part of the cycle of p orbitals. As a result, pyrrole is a planar molecule with a cycle of p orbitals that extends completely around the ring and that contains 6 electrons, so it is aromatic. The p orbitals are not shown in the model below, but each atom has a p orbital that is perpendicular to the plane of the atoms. These parallel p orbitals form an overlapping cycle that extends completely around the ring.
