A review of the fundamental aspects of chemisorbed self‐assembled monolayers (SAMs), as a tool for building complex molecular systems on solid surfaces, is presented. Using alkanethiols, SAMs, as model systems the self‐assembly, surface structures, and SAM stability under different experimental conditions are discussed. We also point out the characteristics of SAMs that make them suitable especially for building active micro‐ and nanostructured molecular systems on surfaces, and stress their limitations resulting from defects, contaminants, and disorder. Finally, we show examples of interfacial architectures drawn from supramolecular and covalent systems to illustrate the potential of SAMs as robust platforms for building functional 3D structures on solid substrates.