For decades, the fields of physics and chemistry have maintained that the atoms and molecules that make up the natural world define the character of solid matter. Salt crystals get their crystalline quality from the ionic bond between sodium and chloride ions, metals like iron or copper get their strength from the metallic bonds between iron or copper atoms, and rubbers get their stretchiness from the flexible bonds within polymers that constitute the rubber. The same principle applies for materials like fungi, bacteria, and wood.