Reproduction is a key step in any organism’s life cycle and its success relies on complex gene regulation. The fusion of highly specialized cells, the gametes, generate a totipotent embryo. We are studying the molecular mechanisms that regulate epigenetic marks, especially DNA methylation, transmission during sexual reproduction in the model plant Arabidopsis thaliana. As epigenetic marks can be modified by environmental factors, it is important to understand how DNA methylation is stably maintained while still allowing diversity in plants and other sexual organisms. We are also particularly interested in how small RNA molecules could act as a link between environmental stresses and transgenerational epigenetic changes.