Cellular rebuilders, found at many large Terran hospitals serving clients with alpha-level insurance coverage, are modified amnio tanks. Clients suffering from serious injury or organ failure are put into an induced coma, connected to a placentium, then immersed in the rebuilder tank where reconstruction at a cellular level is performed under nanobotic control.
Amnio tanks range in size from the one-pint “Digigrow” found in many doctor's offices as an outpatient service, to the converted dry dock at Anchorage Naval Yards currently being used as part of the Ocean Phoenix whale revival project.
The amnio tanks used by the Avatar Project are unusually large, to accommodate the Na’vi-like creatures they are built to create. A standard human amnio tank is about 2.2 meters long and holds about 570 liters of fluid. An avatar tank is 385.82 centimeters long, 148.4 centimeters long, and holds nearly 6,350 liters of fluid. In addition, the avatar tanks are designed to be portable, since most avatar growth takes place on the interstellar vehicle during transit to Pandora.
Thanks to the long duration of the journey (almost six years Earth time), less aggressive growth stimulants are needed to bring the avatar to full adult stature than would usually be necessary; most organisms grown in amnio tanks on Earth are completed within six months.
More “natural” growth to full size of avatars meant that research essentially duplicating the types of experiments carried out on terrestrial mammals did not have to be performed, and also reduced the complexity of the amnio tank monitoring system.
An indication of the differences between Earth organisms and those found on Pandora is given by the composition of the fluid in the amnio tank – the avatar amnio fluid is a relatively strong alkali solution rather than the simple saline that is the base of terrestrial amnio fluids. Indeed, it is so strong that most Earth organisms would be largely dissolved by a few weeks of immersion, and human technicians decanting fully matured avatars are required to wear gloves and protective eyewear during the process. Xenobiologists have discovered that avatar amnio fluid reflects the composition of Pandora’s oceans, which are also somewhat caustic.