Time Spheres are transportable containment spheres used in time travel, in order to make the process easier.
Cisco Ramon created a Time Sphere for Eobard Thawne, who was to travel through a wormhole back to his own time. Ronnie Raymond noted that it included tungsten, known for both the highest melting point of all metals and for having flammable dust that could potentially melt a hole, causing an explosion. In order to prevent this, Eobard suggested that Cisco cement the tiles of the sphere with a cobalt resin to prevent degradation in cases of extreme heat. Despite its creation, Barry Allen torpedoed back through the wormhole, smashing the sphere and disabling Eobard from traveling through time.
Rip Hunter designed the first Time Sphere at some point in the future and the designs of which were obtained by Eobard, who would eventually use them to make the 21st century version.
In 1987, Eobard Thawne obtained a Time Sphere through to unknown means. Eobard Thawne insisted that he and Damien Darhk both change their destinies by traveling to the future and stopping what happened to them so they could acquire a new destiny. Damien Darhk entered the Time Sphere and Eobard Thawne circulated around it, propelling itself off the ground. By doing this, the Speed Force opened and Thawne along with Darhk entered it, traveling to the future.
At some point in the future, after awakening from her coma, Grace Gibbons stole the time sphere Cisco had built for Thawne in 2015 from the Starchives. She subsequently used it to travel back to 2019, hoping to aid her uncle in his mission to exterminate all meta-humans, as well as kill the meta-human who'd been responsible for her parents' deaths.
The day after future Grace's arrival, the future time sphere is detected by Team Flash, who assumed that a Starchives asset was stolen. Cisco and Sherloque breach to the future time sphere's location in the forest while Iris West and Ralph Dibny find the present day time sphere gathering dust in the Starchives. Suspecting these time spheres were one and the same, Cisco had Iris carve a lightning bolt scratch on the present day version, which concurrently appeared on the future version, leading Team Flash to deduce that the new Cicada was the future Grace Gibbons. Joe West noted they couldn't destroy the present day time sphere to stop future Grace without messing up the timeline.
After Barry banished Nora back to 2049, forbidding her from coming back to 2019 again, Iris and Ralph used the time sphere to travel to the future to bring Nora home. Unfortunately, since Nora went into the Negative Speed Force, they were forced to return without her.