This work centers on the study of theory and application of functional differential equations. These are characterized by differential equations in which the derivative of the state at any time depends not only on the state at that time but upon the history of the state up to the present Specific activities of this project will be to learn semigroup and evolution approaches to current investigations on nonlinear and nonautonomous equations used in modeling age- dependent population dynamics and in understanding the biological processes involved in describing cell populations.