Its size does not exceed one millimeter. However, the tardigrade is the most resistant animal on the planet. Nicknamed the water bear, this animal is the only living being known to date that survives a dose of X-rays that exceeds 570,000 rads. For comparison, a human dies at 500 rad. His incredible physical abilities also allow him to withstand extreme temperatures, ranging from +698F to -459,4F. Photo credit: Oliver Meckes