DGLG focuses its activities on Earth and environmental sciences, which means a broad scope of interests. The experimental approach using 'isotope geology' is original and unique in Flanders. The department' labs host several mass spectrometers for the precise determination of several key isotopic systems. The isotopes are powerful geological tools, with a broad range of application, often resulting in stimulating inter-university projects and international collaborations. What can isotopes bring about to the knowledge of geologic and environmental processes? Fractionation processes affecting the light isotopes (O, N, C, H, S) are important in many field of Earth and environmental sciences. They can permit to identify past climatic changes, or physico-chemical modification affection low and high temperature geolological systems. The stable isotope signature can also be used as a tracer of various processes in hydrogeology for example or to characterize organic matter in sediments. But these techniques also have applications in other fields from medical sciences to the food industry for example. Geochronology is based on a radioactive-radiogenic isotope pairs, in the present case K40 and Ar40 (K-Ar and Ar-Ar methods). This versatile method allows the numerical dating of rocks older than the Earth (4.6 billion years) to the eruption of the Vesuvius in roman times (-79 BC). Geochronology is of paramount importance in many geological questions from calibrating the stratigraphic time scale to the timing of various volcanic events.