Electrons confined to one-dimensional (1d) materials offer fascinating opportunities for applications and fundamental studies. Our group uses individually-contacted carbon nanotubes (CNTs) as a model experimental system to investigate these electrons dancing on strings. I will discuss application areas including sensors, quantum light sources, transistors, and photovoltaics. The unique features of CNTs include sensors that detect single electrons, light-emitting diodes that emit single photons on demand, band gaps that are driven by tunable Coulomb interactions, and photovoltaic devices with extraordinary quantum efficiency. Beyond our application-driven research, we also explore the fundamental realm. I will discuss measurements of quantum interference effects, and the compressibility of "electron crystals" that form at low temperature and low electron density.