New book on Derivations in rings. The theory of derivations and automorphisms plays an important role t only in ring theory, but also in functional analysis, linear differential equations concerning the question of innerness and outerness, for instance, the classical Noether-Skolem theorem yields the solution of the problem for finite dimensional central simple algebras. At places, examples are provided to justify the conditions imposed on the hypothesis of various results. Also suitable remarks are given sometime to explain the theory and sometime to conjecture the possible extensions of the results. In the end, an exhaustive references of the existing material related to the subject matter of our thesis is included which may serve as source material for those, interested in the domain of our research.