The flow of ice sheets is controlled by processes occurring at their surface, base and by the spatial variation of rheological properties within the ice. The internal structure of ice sheets represents an integrated memory of the interaction of these processes and properties, knowledge of which has key implications for unraveling history and predicting future behaviour. Numerical models are routinely employed to understand and reproduce the flow of ice. However, models substantially rely on a number of simplyfing assumptions. Despite - partly also because of - the increasing sophistication of models in-situ observations are necessary to reduce the number and fix values of free parameters controlling flow. The most direct way to obtain in-situ properties within the ice is drilling ice cores. However, this is a labour intensive expensive task, which only provides information for a single point, albeit in very high resolution. Active geophysical methods, in contrast, are employed from above the ice surface, thus enableing to cover larger areas in a comparably short amount of time. Laterally imaging the layer architecture of ice sheets yields complementary information to the direct evidence of physical properties otherwise solely provided by ice cores. This talk gives an overview of the state of the art applied geophysics in glaciology, with an emphasis on active seismic and electromagnetic sounding methods. It is shown how these methods provide insights into the distribution of physical properties, stratigraphy, structure and subglacial conditions. An emphasis is put on the role of crystal orientation fabrics (COF) in ice flow and geophysics as an example how numerical flow modeling and geophysics should be fruitfully combined for a mutual benefit and how this could lead to data assimilation in ice-flow models.