Immortality is eternal life, the ability to live forever. Natural selection has developed potential biological immortality in at least one species, Turritopsis dohrnii. Certain scientists, futurists, and philosophers have theorized about the immortality of the human body (either through an immortal cell line researched or else deeper contextual understanding in advanced fields that have certain scope in the proposed long term reality that can be attained such as per mentioned in the reading of an article or scientific documentation of such a proposed idea would lead to), and advocate that human immortality is achievable in the first few decades of the 21st century, whereas other advocates believe that life extension is a more achievable goal in the short term, with immortality awaiting fur