Matter

thumb|Atomic force microscopy (AFM) image of a PTCDA molecule, in which the five six-carbon rings are visible thumb|A scanning tunneling microscopy image of [[pentacene molecules, which consist of linear chains of five carbon rings]] thumb|AFM image of 1,5,9-trioxo-13-azatriangulene and its chemical structure

thumb|Hydrogen in its plasma state is the most abundant ordinary matter in the universe.

In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by pressing or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, hardness can be measured i

aspect of wave–particle duality

boundary between different phases of matter

thumb|Debris still present 10 days after the Joplin tornado struck the city of [[Joplin, Missouri.]]