Recently a number of works have given interesting results on the penumbral fine structure of sunpots (del Toro Iniesta, Bellot Rubio & Collados 2001; Schlichenmaier & Collados 2002), where, for instance, cold supersonic Evershed downflows were observed. In addition, there are recent results that show the existence of shock wave trains propagating in umbral chromospheres with a 3-min period, where the photospheric driving signal has also been detected. The phase difference between the photospheric and chromospheric signals in the 5.5-6.5 mHz band (3 minute) allows to infer that an upward propagation of the slow magnetoacoustic mode, with an increasing velocity amplitude (due to the rapid decrease of density) and reaching the non-linear regime, is giving rise to shock fronts. All these results show that the umbra and the penumbra have a dynamical behaviour which is far from being near an equilibrium situation.