The Healing Tank is a device with medical properties, filled with a liquid, that can completely heal a person from critical injuries.
During a dangerous training scenario on Dervani, Nebula and Gamora engaged each other in fierce combat in a competition to retrieve a data ingot for Ronan. After Nebula was severely injured in a fall, she was treated inside a Healing Tank and forced to undergo cybernetic augmentations.
During another mission against a group of G'rek Raiders in the Orex II Gravity Well, both Nebula and Gamora were forced to set their ship to self-destruct and eject from it, waiting to be picked up. However, after being injured in the ensuing explosion, both women had to be put inside Healing Tanks to recover from their wounds.
The third time Nebula had to be treated inside a Healing Tank was after she was forced to cut off her own arm to free herself from a Laser Thorn Energy Net in Praxius IX. This amputation forced Nebula to undergo a massive cybernetic augmentation in order to turn her weakness into strength.