In the absence of a circulatory system, the flesh uses a system of "nanobots" which maintain the skin. It is unknown what biological processes take place to sustain the flesh covering, since Terminators do not require the consumption of food. Under 2007-era analysis, this blood is shown to be similar to human blood, using a synthetic oxygen carrier rather than human red blood cells, as Terminator endoskeletons contain no bone marrow. Terminator flesh heals by itself, and at a much faster rate than normal human tissue and has never been shown to bruise or discolor from trauma, even after several days. However, a Terminator's flesh covering can die if it sustains adequately massive damage without maintenance, at which point it takes on a waxy, corpse-like pallor and begins to decompose. In Terminator Genisys, it is also shown that a T-800's covering ages; Pops is shown as having aged over eleven years and then a further thirty-three. In Terminator: Dark Fate, the Terminator that killed John Connor visibly aged over the course of the twenty years between the assassination and when it was rediscovered by Sarah Connor, though not as much as Pops had. In addition, its skin covering aging over time allowed it to blend in undetected all that time as a human with a human family. By contrast, a T-888's undamaged flesh can remain un-aging for decades; Myron Stark immured itself for 89 years, emerging from its wall unchanged. Although clearly not the normal procedure, a bare T-800 endoskeleton is able to grow itself a new flesh covering using 2007 technology (with the assistance of a geneticist and its own knowledge of future formulae) by submerging itself in a blood-like bath. This improvised process results in a deformed covering that has the appearance of a burn victim and lacks its own biological eyes, requiring it to steal some and subsequently undergo cosmetic surgery to produce a more normal appearance (while escaping detection from law enforcement as it was able to undergo this procedure without the use of pain medication). Whether or not this replacement flesh possessed the T-800's original flesh's un-aging properties, it appeared healthy despite the T-800's deactivation for many days. The theft of the eyes suggests that Terminator flesh is capable of accepting some degree of organ grafts from ordinary humans, that it can circumvent transplant rejection, and is capable of sustaining the life of the grafted