Tesseract

The Tesseract is an Infinity Stone of unparalleled power that was once owned by Odin. The cube is based on the Cosmic Cube in the Marvel Comics continuity. It exists in the Marvel Cinematic Universe and features predominantly in Captain America: The First Avenger and The Avengers.

Captain America: The First Avenger
It was guarded by the Asgardians, the jewel of Odin's treasure room of relics, but lost during the last age of worship by men on Earth. It is found centuries later in the 1940's by Johann Schmidt (German SS officer and leader of HYDRA) in a box behind Nidhogg in a sculptured mural of yggdrasil world tree, in a church full of Viking warriors entombed within its walls. Schmidt and scientist Arnim Zola used the power of the Tesseract to create weapons against the Allies and the entire world. Captain America foils Schmidt's plan to launch an aerial attack on the United States, and Schmidt disintegrates into light that shoots into space when he touches the Cube. After Captain America crashes Schmidt's plane, the Cube is recovered by Howard Stark.

Iron Man 2
While Tony Stark is flipping through his father's note book, a drawing of a hypercube is briefly seen on one of the pages, possibly alluding to further studies of the cube after recovering it from the Atlantic Ocean.

Thor
A book on Norse mythology featuring illustrations of the Norse gods shows Odin holding an object that seems to be the Tesseract. Years after being lost in the ocean, the cube is now in the hands of S.H.I.E.L.D.. Nick Fury, believing it to be a powerful energy source, recruits Professor Selvig to study it.

The Avengers
After falling into the abyss of space, Loki eventually comes into contact with the alien race of the Chitauri and their masters, Thanos and his servant "The Other". Loki promises to retrieve the Tesseract from Earth and give it to them in exchange for their army.

Around this time, S.H.I.E.L.D. is planning to use the Tesseract to create weapons of mass destruction so Earth can defend itself in the event of an attack by enemies from other worlds. This was due to the battle between Thor and Loki, however, according to Thor, their work with the Tesseract was what drew Loki and the Chitauri to it.

After Fury has recruited Dr. Selvig to study the Tesseract, he has now been notified that it is "misbehaving". Fury arrives at a Project P.E.G.A.S.U.S. where the Tesseract opens a portal into space and transports Loki to the S.H.I.E.L.D. base. Loki immediately begins slaughtering S.H.I.E.L.D. agents and reveals that he plans to use the Tesseract to enslave the human race. The residual energy of the portal causes an explosion, collapsing the entire facility into a huge pit.

After escaping, Loki has the now mind-controlled Dr. Selvig work on a device which will allow the Tesseract to open a portal through which the Chitauri will invade Earth.

As instructed by Agent Coulson, Natasha Romanoff recruits Bruce Banner to trace the Tesseract through its emission of low-level gamma radiation that only he would be able to trace. Coulson visits Tony Stark, leaving material which convinces Stark to join the team.

Selvig sets up the Tesseract-powered device atop Stark Tower, opening the portal over New York City for the Chitauri fleet. Later Natasha Romanoff is told by Dr. Selvig, now free from Loki's mind control, that Loki's scepter can close the portal because "she (the Tesseract) can't defend against herself."

The World Security Council override Nick Fury and order a nuclear missile launched on Manhattan, but Iron Man intercepts it and guides it through the portal to destroy the Chitauri base, just as Natasha Romanoff deactivates the portal. Iron Man falls through the portal back to Earth just as it closes.

Thor takes the Tesseract  and Loki back to Asgard. Though his superiors are angry at this turn of events, Nick Fury defends his decision to allow Thor to take the Tesseract, saying that humanity is simply not at a level where it deserves the cube's power. At the same time, it is strongly suggested that Thor and Loki would not have been able to leave Earth unless the Tesseract was used to do so.

Thor: The Dark World Prelude
Thanos is searching for the Tesseract and Loki tells him he can find it.

"0-8-4"
A device was found that is powered by Tesseract technology.

Thor: The Dark World
After recovering the Aether, the Asgardians took it to The Collector and told him the Tesseract was in Asgard and it is "unwise to keep two Infinity Stones in one place."

Powers and Abilities
The Tesseract is one of the most powerful artifacts in the universe. According to Fury, it holds great power that is almost unlimited; Black Widow tells Bruce Banner it has the power to destroy the entire planet.

The Tesseract can open rifts through space and time. This is how Loki transported himself and later, the Chitauri, to Earth through a portal. Thor and a muzzled Loki use the Tesseract to teleport back to Asgard.

It can be used to power other weapons. HYDRA's Tesseract-powered weapons were particularly devastating, as a single shot could completely disintegrate an opponent. Loki's Chitauri scepter also apparently runs on the power of the Tesseract, as implied by Selvig's statement that "she (the Tesseract) can't protect against herself (the scepter)" and Steve Rogers's statement that "it works an awful lot like a HYDRA weapon."

Besides its use as a weapon, the device can harness and channel a seemingly unimaginable amount of field quanta to protect itself from being attacked by other energy sources, as seen when the field region, surrounding the tesseract, proved to be completely impervious to Iron Man's repulsor beams. This prompted Jarvis to state that the cube's barrier is "pure energy", confirmed in one way or another by Loki and Thor on later occasion.

The Tesseract can also show visions of the future, which may or may not come true. The people who have seen this power are the Red Skull, Eric Selvig, and Hawkeye, when the latter two were under the control of the Chitauri scepter.

It cannot be held by mortal hands. Any mortal who does so will be disintegrated, their remains sent to another world, as evidenced with what happened to Red Skull. Fury very briefly touched it to move it with gloved hands, and had to drop it very quickly. (While the Tesseract is shown to burn living flesh, it apparently has no effect on dead wood - it was stored safely in a wooden compartment for centuries.)

The Tesseract is one of six Infinity Stones. It is the Space Stone.

Appearances

 * Marvel Cinematic Universe (5 films)
 * Captain America: The First Avenger
 * Iron Man 2 (first appearance)
 * Thor
 * The Avengers
 * Thor: The Dark World (Mentioned only)
 * Marvel Cinematic Universe (1 TV series)
 * Agents of S.H.I.E.L.D.
 * "0-8-4" (Mentioned only)
 * Marvel Cinematic Universe (1 comic)
 * Thor: The Dark World Prelude

Behind the scenes
To be added

Trivia

 * It is based on the Cosmic Cube from the Marvel Comics continuity.  The first Cosmic Cube was created by AIM, though the origins of the Tesseract are unknown.  While it's known that the Tesseract was possessed and used by Asgardians before it was hidden in Tonsberg, Norway, it's never stated that the Asgardians actually created it.
 * A replica of Tesseract is a pre-order bonus for the Phase One - Avengers Assembled Blu-ray. When placed in the S.H.I.E.L.D. briefcase, it glows.
 * A Tesseract, commonly called a hypercube, is a 4-dimensional cube. The Tesseract shows some possibly "4th dimensional" qualities, such as: teleporting objects, seemingly through a fourth dimension; being able to call up massive amounts of cosmic energy, seemingly out of another dimension; Howard Stark draws the Hypercube as a four dimensional cube, as a cube within and connected to a larger cube (see pic. in gallery).
 * The post-credits scene in Thor: The Dark World reveals that the film's central weapon, the "Aether", is one of six "Infinity Stones", and that the Tesseract from the previous films Captain America: The First Avenger and The Avengers is another. It is also noted that it would be unwise to keep two of the stones in the same location.
 * Also in Thor: The Dark World, Jane Foster describes the healing procedure, provided by Asgardian technology, as some kind of 'quantum field' control. This might be a feature, derived from studies on the tesseract, when it was in Asgard, prior to its arrival on Earth.