The most interesting aspect about human beings is our ability to evolve. Scientists believe that our entire species may have slowly evolved from nothing more than microscopic single-cell organisms. Mankind was once so new to this world that the most advanced discovery for us was learning how to build a fire. Now, we have the ability to control entire cities and countries without moving an inch.
The individual unit of a species acts in a fashion that is not very different from the way it behaves as a whole. So, in the very manner that our species has evolved as a whole, we too, evolve individually from the moment we are born. We call this evolution, growth.