The Infinity Stones - as explained by the Collector in Guardians of the Galaxy - are singularities left over from the Big Bang. At the end of Avengers: Age of Ultron, Thor points out that several Infinity Stones have shown up in the last few years, five to be exact. Kevin Feige has stated that the remaining stone will be revealed at some point in Phase 3, but when can we expect that and how will it tie in to the story? The five stones that have been uncovered are: The Space Stone , contained within the Tesseract, was hidden on Earth for centuries. Until 1942 when it was taken by the Red Skull, who used it to power his inventions. At the end of the war it was recovered by Howard Stark on behalf of the Strategic Scientific Reserve. It remained in the custody of S.H.I.E.L.D. until Loki stole it and used it to open a portal to the other side of the galaxy in an attempt to take over the world. Whereas Loki's goal was to rule Earth, his benefactor/Boss Thanos, had bigger plans