Organic functional thin-film materials are expected to be applied to various kinds of photonic/electronic devices, such as nonlinear optical circuits, photovoltaic devices, electroluminescent devices, thin-film transistors, and bio/medical-photonic devices. In order to realize high-performance thin-film photonic and electronic materials, control of dimensionality and wavefunction shapes by designated arrangements of molecules in the thin films is essential. In Molecular layer deposition (MLD), different kinds of molecules are introduced onto a substrate surface with designated sequences to achieve monomolecular step growth of polymer wires or molecular wires using the self-limiting effect. MLD enables self-organized growth of polymer/molecular wire networks with designated molecular sequences, locations, and orientations. MLD in the liquid phase is expected to contribute to biomedical fields including selective attack on cancer cells. The chapter also presents an overview of the key concepts discussed in this book.