This paper covers four specific areas—diverse in their scope and approach—of nanophotonics research at Bell Labs, ranging from nanosized light emitters to passive and active optical circuits fabricated or actuated with nanometer precision. Our first example involves the dynamics of carriers confined in quantum dots fabricated via self-assembly on semiconducting substrates; we show that the evolution of carrier populations is a result of the interplay of interactions between photons, phonons, electrons, and holes. A second example involves a nanosize light-emitting quantum dot system that is fabricated by embedding passivated spherical semiconducting quantum dots in a polymer matrix; the fabrication steps and subsequent optical measurements, including the observation of net optical gain in this system, are described. In the area of passive and active optical circuits, we report on efforts to optimize the transmission efficiencies of photonic crystal circuit-building elements (e.g., waveguide bends and waveguide tapers in passive two-dimensional photonic crystal circuits). Finally, we describe active optical silicon circuits fabricated on a silicon-on-insulator platform; these devices comprise waveguide interferometers and electrostatically actuated piston micromirrors, and they require nanometer-size displacements to function as optical switches with inherently low power consumption. © 2005 Lucent Technologies Inc.