The optical model potential (OMP) constitutes one of the primary tools for studying and interpreting nuclear scattering data. From first principles, this one-body operator can formally be identified with the mass operator in the Dyson expansion of the oneparticle Green function. The use of the Brueckner-Bethe-Goldstone G-matrix and simplifying assumptions on its the momentum- and/or coordinate-space structure has allowed the realization of efficient forms for the OMP, providing reasonably good description of a broad body of scattering data. However, remaining discrepancies call for a closer scrutiny of the various contributions leading to the first-order term. In this seminar we review some general aspects of the OMP, particularly its momentum- and coordinate-space structures. It will be shown that the intrinsic medium effects of the NN effective interaction can be disentangled from those in free space. This feature leads to surface-peaked contributions of the g-matrix in the evaluation of the optical potential. The scope of these findings on ongoing and future research will be discussed.