single-walled nanotubes (swnts) were first seen in 1993 as cylinders rolled from a single graphene sheet. in 1998, the first peapod was observed by brian smith, marc monthioux and david luzzi. the idea of peapods came from the structure that was produced inside a transmission electron microscope in 2000. they were first recognized in fragments obtained by a pulsed-laser vaporization synthesis followed by treatment with an acid and annealing.