Hasan Sahin visits the Material Science Institute of Madrid for a seminar about Understanding 2D Materials Based Chemosensors via Theory and Experiments. His talk is about chemosensors where graphene and similar two-dimensional crystal materials are used as a sensing surface. Chemosensors are tools used effectively, especially for the separation of organic molecules. An atomic scale understanding of the experimental data we have recently obtained has been achieved using theoretical calculations. How molecules that are very similar to each other can be distinguished and the effect of the surface synthesis method on sensor behavior are the topics he told us about in his speech.