Terrigenesis

Terrigenesis refers to a biological process that occurs after one is exposed to the chemical compound known as Terrigen. When it interacts with the physiology of a humanoid experiment dubbed an Inhuman, it has the effect of activating the being's dormant superhuman potential. Only humans gifted with the Inhuman gene benefit from this effect. To normal human beings, Terrigen is fatal. Exposure to it causes the body to transform into a black mineral substance and then crumbles to dust. Terrigen exists in a gaseous form, but can be solidified wherein it takes on a crystalline structure. These blue-colored samples of solidified Terrigen are commonly referred to as Terrigen crystals.

S.H.I.E.L.D. agents Phil Coulson and Alphonso Mackenzie were fighting an Inhuman teleporter named Gordon, who was in possession of one such Crystal. After Gordon was killed, he dropped the crystal, but Coulson leaped forward to catch it before it could shatter on the floor, thus making the Terrigen Mist airborne. Contact with the crystal began to transmutate his right hand until Mack cut it off with an axe.

Large quantities of Terrigen were dumped into the ocean and thus were spread through the ecosystem, though it seemed to effect only humans. Members of Earth's intelligence agency, S.H.I.E.L.D. have worked extensively to understand Terrigen's effects on human biology.

A scientist named Holden Radcliffe was coerced by the Inhuman progenitor Hive to make advancements in the Terrigenesis effect in order to create an army for him. This process worked on ordinary humans, but instead of gifting each of them with unique abilities, it transformed them into grotesque creatures that were subservient to Hive's commands. They were referred to as Primitives, or Alpha Primitives.