Early detection of disseminated cancer cells in metastatic niches such as the bone marrow is currently a highly complex challenge. Breast cancer cells that have abandoned their primary tumour tend to enter a dormant state once they reach these metastatic niches. In this context, there is an urgent need to develop new controlled and accessible in vitro models capable of mimicking the 3D microenvironment of these dormant cancer cells to analyse their interaction with the ECM. In this project, 3D hydrogels and 3D-printed scaffolds, all based on biomaterials, will be designed and fabricated to mimic the bone marrow microenvironment and, consequently, the bone, allowing a controlled analysis of the interaction between breast cancer cells and the matrix. As a result of this project, vital insights are expected to be obtained to develop new therapeutic strategies targeting dormant cancer cells and their microenvironment, and consequently early metastatic stages.