This is an atomic structure of graphite. Graphite is a layered material made of carbon atoms, and a pencil lead is made of graphite.

By printing this material, you can understand the characteristics of graphite structure such as:

• a single layer has honeycomb structure which is due to the sp2 bondings between carbon atoms,
• interlayer distance is much larger than intralayer distance. This is because the interlayer coupling is not covalent bonding but the van der Waals interaction (or intermolecular force),
• so, you can feel a van der Waals world by this material.

The stl file is made by Blender.