We report the synthesis of single-crystalline silver nanowires of atomic dimensions. The uttrathin silver wires with 0.4 nanometer width grow up to micrometer-scale length inside the pores of self-assembled calix[4]hydroquinone nanotubes by etectro-/photochemical redox reaction in an ambient aqueous phase. The present subnanowires are very stable under ambient air and aqueous environments, unlike previously reported metal wires of similar to1 nanometer diameter, which existed only transiently in ultrahigh vacuum. The wires exist as coherently oriented three-dimensional arrays of ultrahigh density and thus could be used as model systems for investigating one-dimensional phenomena and as nanoconnectors for designing nanoelectronic devices.