This review is devoted to discuss our present understanding of how outflows participate in defining ths various types of morrphologies and featurea observed in Active Galactic Nuclei (AGN). We suggest possÍble interpretations of structurcs observed at radio frequencies (non-thermal continuum radiation) and optical frequencies (continuum and emission line radiation) in terms of results from numerical simulations of outflow propagation and their analytical physical explanation. The conclusion is that we have already reached a good qualitative knowledge oř the several dynamical effects which shape AGN’s structures; the quantitative estimate of their relative importance and conditions of occurrence still awaits a better study of the nonlinear processes in astrophysical conditions and more observational data to determine the values of the physical parameters.
The non-thermal spectra of many extragalactic jets and active galactic nuclei have a power law form over many orders of magnitudes. This kind of spectrum is assumed to be the result of shock acceleration of relativistic elcctrons at these sources.
As observed by Rieke et al. (1982) some of the A.G.N's, especially the BL Lac type, have an abrupt cutoff at IR-V frequencies. In some cases the intensity of the non-thermal radiation decreases by
more than two orders of magnitude over a frequency band of less than one order of magnitude.