Our group is working on the role of the microenvironment in the initiation and maintenance of hematological malignancies. The prerequisite for coordinated hematopoiesis is an intact function of hematopoietic stem cells, which is strictly regulated by the bone marrow niche. The hematopoietic stem cell niche is characterized by a complex composition of cellular and non-cellular constituents. For many hematological neoplasms, we are gaining an increasingly better understanding of the structural and functional changes within the bone marrow niche and their significance for leukemogenesis. Finally, by uncovering the underlying mechanisms, we aim at disrupting the interaction of malignant cells with their microenvironment to finally eradicate leukemia-initiating cells.