Systems Theory is a transdisciplinary field that involves complex combinations of different research fields with the purpose to explain the observed natural phenomena in the world around us. This field results in the appearance of the General System Theory. The aim of the present book is to present some of what is being done, in the 21st century, in different fields that comprise the Systems Theory. In the several chapters of this book developments of this theory are presented with the aim to solve different problems of systems. Different areas are covered, from biology and psychology to electronics, information sciences and management. The authors present their research in the study of the synthetic and systems biology, systems theory of bipolar disorder, unifying principles of science through physical activities, control of linear and non-linear systems, class of superquadratic Hamiltonian systems, systems with propagation, wireless sensor networks, information systems, and service operations management. This book is a tool composed by several results in the systems theory of several research fields with important application in the resolution of the problem of understanding our world.