From the Technology Review, a cautionary emphasis on the early state of this regenerative research: "Experts say the findings are exciting, but they caution that much remains to be done before new limbs can be grown in mammals. The studies took place in still-developing animals, whose cells are likely much more flexible when it comes to inducing regeneration ... Even mammals, including humans, show some regenerative capabilities. Under some circumstances, children as old as five can grow a new fingertip if the wound is treated correctly. But that ability is lost as we age. [The Wnt signalling pathway] is undoubtedly a critical one. But other unknown factors are probably needed to reactivate adult, fully differentiated tissue to reconstruct a new structure ... regeneration in mammals will likely require inhibition of our normal immune response, which triggers inflammation at the site of a wound. None of the animals that can regenerate limbs show this type of immune response."