https://phys.org/news/2018-08-d-strongest-materials-earth.html

Because of its strength—graphene is one of the strongest materials ever tested on Earth—and its high thermal and electricity conductivity, 3-D printed graphene objects would be highly coveted in certain industries, including batteries, aerospace, separation, heat management, sensors, and catalysis.

Graphene is a single layer of carbon atoms organized in a hexagonal lattice. When graphene sheets are neatly stacked on top of each other and formed into a three-dimensional shape, it becomes graphite, commonly known as the "lead" in pencils.