Life on Earth comes in an astonishing number of forms, shapes and sizes. The evolution of a notochord not only acted as structural support to some of the earliest invertebrate chordates; it also provided a site for muscle attachment and is the precursor for vertebral development. Aside from being a crucial process that forms the solid backbone for you and I to stand upright; it also allows vertebrates to grow larger without needing to deal with issues that stemmed from having an exoskeleton. These include periodic vulnerability post-molt and a self-limiting factor that prevented parts of the body from growing too thick and too heavy during growth, since doubling the body size of any object would increase its mass and volume by a factor of eight while the ability to support itself will only be increased by a factor of four (Square-cube law). This is why most if not all of the largest animals ever lived come from the Chordata phylum and are almost always vertebrates.