Blood is created in bone marrow and is made up of cells suspended in liquid plasma. Red blood cells carry oxygen, white blood cells fight infection, and platelets are cell fragments that allow blood to clot.

Deoxyribonucleic acid (DNA) is the molecule that contains genetic information. DNA is encoded through a combination of nucleotides that bind together in a specific double helix pattern.

The broadest classification of life splits all organisms into three groups called domains. The three domains of life are bacteria, archaea and eukaryota.

The Earth's rocks fall into three categories based on how they're formed. Igneous rock (granite, basalt, obsidian) is formed from the hardening of molten rock (lava), sedimentary rock (shale, sandstone, coal) is formed by the gradual despositing and cementing of rock and other debris, and metamorphic rock (marble, slate, quartzite) which is formed when existing rock is altered though pressure, temperature, or chemical processes.