Guanosine (GMP) is the ideal brick for controlled self-assembly of biocompatible materials, as it has the ability to self-associate in water to form G-quartets (G4), and four stranded structures, termed G-quadruplexes (G4n). Recently we have studied on NIMROD (RB1810131) its hydration properties at concentrations of 0.117 M and 0.132 M and found that at the lowest concentrations GMP molecules are well hydrated and apart one from each other. Conversely, at the highest concentration we have found clear evidence for G4 aggregates, with structure compatible with NMR data. We request beam time on NIMROD in order to complete the study with an experiment on highly concentrated GMP solutions in 1 M KCl+water, where G4n aggregates are predominant, in order to extract the structure and hydration of G4n units and shed light on the role of hydrophobic/hydrophilic interactions in self-assembling.