The lateral membrane structure at molecular length scales is accessible via the grazing incidence diffraction (GID) scattering geometry, at which the 2D detector (CCD camera) is moved out of the plane of incidence at grazing incidence and exit angles. The lipid chain correlation peak (Fig. 1v) is usually stretched around a circle with the radius q = (q k 2 ? q z 2 ) 1/2 % 1.4 Å -1 reflecting the distribution of acyl chain tilt angles with respect to the bilayer normal. The radial profile of the peak has a Lorentzian lineshape with a peak position corresponding to the inverse nearestneighbor distance of chains and its width reflecting the lateral correlation length (see below). This peak is often broadened upon peptide insertion. A lateral correlation of membrane-inserted structures, e.g., a regular oligomerization as known from pore arrangements, can be detected and characterized from ''superstructure peaks'' (Constantin et al. 2007 ) in the small-angle region at low q z (Fig. 1vi ). In addition, the conformation of the reconstituted peptide's structure can in some cases be deduced from the low q k signal of molecular form factors, the so-called helix maximum (Fig. 1vii) , or from helix peaks revealing intrahelical distances at high q k (not shown) as it has been revealed for the regularly organized and conformationally constrained alamethicin single helix (Spaar and Salditt 2003) .