The inversion of thousands of p-modes, identified with great accuracy, has clearly demonstrated the substantial correctness of the standard solar models. The use of the new equation of state and opacity tables, together with the element diffusion towards the central regions of the Sun, has allowed the construction of solar models which are consistent with helioseismology within 1%. This result, combined with the neutrino fluxes measured by the four exsisting experiments and some nuclear reaction model-independent constraints, seems to exclude the possibility that the neutrino problem is astrophysical in origin, but it should rely upon non standard neutrino properties, as the MSW effect. The internal dynamics of the Sun are deduced from the inversion of p-mode rotational splittings which has revealed unexpected features in the distribution of the angular velocity in the convection zone and in the underlying radiative envelope from the base of the convection zone to a depth of 0.3 R ⊙. This poses severe constraints on the location of the solar cycle generation mechanism and the evolution of the solar angular momentum. Only recently, full operation of the helioseismic networks IRIS and BISON has allowed us to measure the lowest degree p-mode splittings and to infer the rotation of the central regions of the Sun below 0.3 R ⊙, though with contradictory results. While the p-mode analysis gives a reliable picture of the real Sun, except in the innermost regions where only average properties can be deduced, the detailed knowledge of the structural and dynamical properties of the solar core will only be possible by means of the detection and identification of g-modes, if they are really excited in the Sun, from the forthcoming data of the GOLF instrument on the SOHO satellite.