Electrodeposition (ED) and chemical bath deposition (CBD) are both solution processing methods that assemble solid materials from molecules, ions, or complexes in solution. The reactions occur on solid surfaces to produce polycrystalline and epitaxial films, porous networks, nanorods, superlattices, and composites. Both methods can be used to produce metals, semiconductors, magnetic materials, and ceramics in a wide array of architectures. Because of the low processing temperatures (often near room temperature), the techniques are ideal for producing nanostructured materials and interfaces. The methods are not only inexpensive and relatively simple, but they can often produce materials and nanostructures that cannot be accessed in ultrahigh vacuum. For example, the shape and orientation can be tuned by controlling the pH or through solution additives. Also, in ED, the departure from equilibrium can be precisely controlled through the applied potential. This issue attempts to provide understanding of the growth mechanisms—from the molecular to final structure—of interfacial electrochemical and CBD reactions. For example, the influence of solution additives and pH and the effect of external parameters such as the applied potential will be discussed. Practical applications of these films and nanostructures include photovoltaic/photoelectrochemical cells and chemical/magnetic sensors.