Polysaccharides are the most abundant organic materials in nature, yet correlations between their three-dimensional structure and macroscopic properties have not been established. Automated glycan assembly enables the preparation of well-defined oligo- and polysaccharides resembling natural as well as unnatural structures. These synthetic glycans are ideal probes for the fundamental study of polysaccharides. According to molecular modeling simulations and NMR analysis, different classes of polysaccharides adopt fundamentally different conformations that are drastically altered by single-site substitutions. Larger synthetic polysaccharides are obtained via a "LEGO"-like approach as a first step toward the production of tailor-made carbohydrate-based materials.