In the eighties, many visionary researchers (Brockett, Isidori, Byrnes, Arstein, Sontag, to cite only a few ones) started studying analysis and control of systems described by nonlinear ordinary differential, or difference equations, trying to avoid any kind of first order linear approximations. The research field revealed soon to be an amazing arena, for a paramount number of researchers all over the world, and involved both engineering and mathematical aspects. The Automatic Control Group of the University of L’Aquila has given many important contributions in the field. For instance, in 1993, an algorithm for the estimation of state variables of nonlinear systems by partial measurements was published, which has been applied successfully to many problems arising from electrical, chemical and biomedical engineering. The group is highly active in the field and offers courses of nonlinear control to students of the Laurea Magistralis in computer science and automatic control, also in english. Significant results have been obtained in the so called regulator problem, in the analysis and control of nonlinear systems with delays in input, output, internal variables. In addition, networked control has given a great impulse to the study of nonlinear systems with delays, which are caused by signal transmissions times. Some of the main topics on which the group is focused, are: polynomial methods for filtering of nonlinear systems affected by gaussian and non gaussian noise; construction of state observers for nonlinear systems with delays in measurements; direct and converse stability criteria for functional nonlinear systems; actuator disturbance attenuation by feedback redesign with input-to-state stability methods; observer-based control of chemical reactors; observer-based control of human glycemia; stability and control of sistems with positive internal variables; construction of discrete event systems, by bi-simulation methodologies; control of electrical motors; automotive control; sampled-data control for nonlinear systems.