The production capacity for carbon nanotubes (CNTs) already reaches a few thousand tons per year, reflecting the global commercial interest in CNTs. Today, bulk CNT powders are used in a variety of commercial items, including rechargeable batteries, automobile components, recreational goods, boat hulls, and water filters. CNTs can now be included into thin-film electronics and large-area coatings due to advances in CNT manufacturing, purification, and chemical modification. CNT yarns and sheets already exhibit promise performance for applications such as supercapacitors, actuators, and lightweight electromagnetic shields, while not yet offering compelling mechanical strength or electrical or thermal conductivities for many applications.