Hydrogels offer ideal environments for biomedical applications, as they provide mechanical support, hydration, viscoelastic properties that are ideally suited to mimic natural tissues and for biocompatibility, as well as the ability to encapsulate and deliver bioactive compounds. Various biomolecular classes can be used as building blocks for promising performance, such as cabrohydrates, proteins, and polypeptides. In particular, self-assembling peptide amphiphiles, and N-capped or uncapped short sequences have attracted researchers' attention for their ease of preparation and ability to fine control their purity and homogeneity, relative to macromolecular gelators of natural origin. Considering that the shorter is a peptide sequence, the lower will be its cost and ease of production, dipeptides stand out as an attractive option, as demonstrated by the well-known Phe-Phe motif, and variations thereof. Furthermore, the inclusion of non-proteogenic D-enantiomers and amino acids with non-natural side chains, such as norleucine (Nle), are attractive strategies to increase peptides' stability in biological environments and to fine-tune their supramolecular behavior. In this work, we show that all possible combinations of Nle and Phe in dipeptides lead to hydrogels that are compatible with cell culture conditions, albeit the supramolecular packing, hence the resulting viscoelastic properties, varies greatly between isomers. The resulting assemblies encompass amphipathic layers and water-channels of varying diameters as they are defined by 4 or 6 dipeptide molecules. This is in marked contrast with Phe-Phe stereoisomers that consistently form water channels defined by 6 peptide molecules, or Leu-Phe and Phe-Leu isomers, whose channels are defined by 4 peptides. Furthermore, the use of synchrotron-radiation techniques allows to pinpoint key intermolecular interactions that are crucial for self-assembly.