An elucidative account regarding the topic of species problem and certain issues as well as challenges related to it have been provided in this book. It is a compilation of theoretical research works regarding the species problem, which is among the most elementary issues in biology. The primary topics covered in this book are: evolutionary emergence of the species as an individual unit of a specific level of generality; consideration of the species problem from the point of view of modern non-conventional science paradigm, with stress on its conceptual status presuming its characterization in the boundaries of specific conceptual framework; a review of the concept of biological species on the basis of the "friend-foe" identification system; considerations of the concepts of phylogenomics and evolution of species as candidates for the universal one; species delimitation approach employing multi-locus coalescent-based technique; epistemological view of the species as a specific explanatory hypotheses; review of species concept proposed by Darwin.