We show that, starting from density‐dependent nucleon‐nucleon interactions (extended Skyrme forces), one is able to construct an interaction that leads to correct saturation properties in the nucleus and also behaves as a good effective interaction in describing low‐lying excitations. This is illustrated in various mass regions. In those regions where many protons and neutrons determine the nuclear structure, one has to resort on collective model descriptions. We shortly point out the importance of symmetry considerations (the Interacting‐Boson model). More in particular, we concentrate on those modes of motion where the interplay of protons and neutrons is dominant: the M1 scissor mode, intruder 0+excitations and shape coexistence. Results for the Cd region, the Pb region and the N=20 nuclei are presented.