Plato associated the octahedron with air, because its minuscule components are so smooth that one can barely feel it.
The octahedron is a platonic solid consists of 8 congruent triangles.
It has 12 edges and 6 vertices. At each vertex 4 faces meet.
It looks like two pyramids with their bases together.
It has 11 possible nets:
To view the 3D version:
https://www.mathsisfun.com/definitions/octahedron.html
How to make the net: