Salamanders secrete mucus from their skin that in some species is sticky or toxic, protecting them from predation. Bright coloration of some salamanders (aposematic coloration) warns predators that they are not edible. If preyed upon, many salamanders can make new body parts. Salamanders are unique among back-boned animals (vertebrates) in regenerating legs or even eyes with no scarring. If attacked by a predator, some salamanders drop off their tails (autotomy). The salamander might escape while the predator focuses on the detached, wiggling tail. In just a few weeks, a new tail grows. Scientists are studying regeneration in axolotl salamanders. A clump of cells (blastema) forms where a limb has been lost. By reverting to an earlier stage of development (when they were less specialized), the cells can grow into skin, bone, muscle, and other tissues to form a new limb. What scientists find may help make human limb regeneration possible someday.