In this joint webinar by NFDI4Chem, NFDI4Cat and NFDI4Ing we introduce the concept of Ontologies and their use in Engineering Sciences, Catalysis and Chemistry. Ontologies can help describe research objects, processes and results in a way that not only humans, but also machines can understand and work with. This opens up amazing possibilities for finding, using and integrating research results. The webinar is aimed at scientists with an interest in, but no prior experience with Ontologies. It provides a have a brief introduction to Ontologies and interesting speakers from academia and industry.