In May 2004, Jackson et al. published an article entitled "Spontaneous assembly of subnanometre-ordered domains in the ligand shell of monolayer-protected nanoparticles". [ 1 ] This was to become the fi rst of a series which now counts over ten research articles. [ 1 , 2 ] All of these are based on the existence of "stripy" nanoparticles, where the stripes are constituted by the self-organization of two different thi-olated ligands. A number of unusual and exciting properties are attributed to the nanoscale organization of the ligands. Thus, stripy nanoparticles are reported as being "extremely effective in avoiding non-specifi c adsorption of a variety of proteins", [ 1 ] having the ability to "penetrate the plasma mem-brane without bilayer disruption" [ 2j ] and having poles which are particularly reactive and can be selectively addressed to obtain divalent nanoparticles. [ 2c ] This series of articles and the corresponding structure–property relationships are impor-tant because of their direct impact on our understanding of several of the key contemporary problems in the fi eld of nanoscience. The latter include the characterization of nano-materials with sub-nanometer resolution, [ 3 ] the possibility of controlling the self-organization of ligands on gold nano-particles, [ 4 ] the understanding of nanoparticle–biomolecule and nanoparticle–cell interactions, [ 5 ] and the intracellular delivery of nanoparticles. [ 6 ] The proposed stripy structure is based on scanning tunneling microscopy (STM) images which have not yet been reproduced by other groups to date. Our interest lies in nanoparticle surface engineering [ 7 ] and the interaction of nanoparticles with living cells. [ 6b ] Carefully following the published results for producing stripy nano-particles, we failed to substantiate a number of the claims made about their properties, so in the fi rst part of this paper we critically revisit the published evidence for stripiness and in the second part we present our own results regarding their physicochemical properties. We fi rst consider a simple geometrical problem. An STM topography image of a spherical particle is, in fi rst approxi-mation, a 2D projection of the top hemisphere. If a spherical particle is covered with regularly spaced stripes, what should be the apparent width of the stripes? For a 5.8 nm-diameter sphere with 18 regularly spaced 1 nm-wide stripes (9 per hemisphere), the width of the projected stripes on a 2D image decreases rapidly as the STM tip goes from the top of the sphere to its edge, perpendicularly to the stripe direction (Figure 1 a). A model theoretical STM image of the 5.8 nm stripy nanoparticle is constructed (Figure 1 b) and a theoret-ical line profi le of it is shown (Figure 1 c). We now compare this model with Jackson et al.'s experi-mental results. [ 1 ] An exemplary STM image of a nanoparticle from their manuscript is shown in Figure 1 d. The diameter of the gold core was measured by the authors as being 3.8 nm (by transmission electron microscopy, TEM). The thickness of the mercaptopropionic acid (MPA)/octanethiol (OT) layer was evaluated to be ∼ 1 nm, and, according to the authors, the stripe periodicity was 1 nm (see Table S1, Supporting Infor-mation, Jackson et al.). The simple geometrical model above therefore applies (3.8 nm + 2x1 nm, i.e., a 5.8 nm-diameter sphere with a 1 nm periodicity) and a strong dependence of the observed stripe width in the STM image is expected (1 nm, 0.9 nm, 0.6 nm, 0.3 nm). This is, however, not what is observed: experimentally, the apparent stripe width does not decrease as the tip moves away from the top of the hemi-sphere (Figure 1 d). The stripe width is constant within ± 10% (Figure 1 e) and other particles have the same characteristics (Figure S1 and Table S1 of our SI). This discrepancy between the geometrical prediction and the experimental results cannot be explained by size polydispersity or a small error in particle sizing: for a particle 20% larger, the geometrical effect would still be very pronounced (1, 0.9, 0.8, 0.6, 0.4, 0.1 nm). The interpretation of Jackson et al.'s STM images as indicating the presence of regularly spaced stripes on the nanoparticles confl icts with geometry: if stripes are regularly spaced in 3D, they cannot be regularly spaced in 2D. Another characteristic of the stripes is that they are aligned perpendicular to the scanning direction (additional