 The human thymus is the primary organ responsible for developing T-cells, which are essential components of the immune system. It has been observed that hematopoietic stem cells, HSCs, which are precursors to all blood cells, migrate to the thymus from the fetal liver and bone marrow after birth. However, the exact mechanisms behind this process remain unclear. In this study, researchers used a three-dimensional microfluidic device to investigate how HSCs move through the thymus. They found that the presence of human thymic stromal cells, TSC, increased the rate of HSC extravasation into the extracellular matrix by up to three times. Additionally, they discovered that the interaction between endothelial cells, thymic epithelial cells, TEC, and interstitial cells, TIC, was important in regulating HSC migration. This study provides insight into the mechanisms involved in HSC migration to the thymus, and could potentially be used to develop treatments for diseases such as autoimmunity. This article was authored by Sarah A. Watson, Yusef Javimardi, Luca Zanieri, and others.