Observations of oscillations on the solar and stellar surfaces have emerged as a unique and extremely powerful tool to gain information on, and understanding of, the processes in the Sun and stars, and the origin of the variability in the solar and stellar output.Through helio- and asteroseismology detailed inferences of the internal structure and rotation of the Sun, and extensive information on the properties of a broad range of stars can be obtained.Space-based observations play a leading role in helio- and asteroseismology, in close synergy with ground-based observations as well as theoretical modelling. Long observing sequences are essential for measuring the oscillation frequencies with the precision required, and to extract the lowest mode frequencies involved. The enormous value of long-term space-based observations has been demonstrated in the solar case by the joint ESA/NASA SOHO mission (Solar and Heliospheric Observatory. This is now being followed by instruments on the NASA Solar Dynamics Observatory (SDO) mission.Large volumes of exquisite data on stellar oscillations of stars with a broad range of masses and ages are being collected by the CNES space mission CoRoT (Convection, Rotation and Transit) and the NASA Kepler mission.Extensive Earth-based observations of solar oscillations have been undertaken with the GONG network (Global Oscillations Network Group) and the Birmingham Oscillation Network (BiSON) to ensure continuous monitoring. A asteroseismic network, SONG (Stellar Observations Network Group) is being established under Danish leadership. Equally important for asteroseismology is the availability of supplementary data on the stars from more traditional observations, to determine their surface temperature, composition, radius, etc. Only through a coordinated use of the space- and ground-based data can the full potential of helio- and asteroseismology be realized.