The research project focusses on designing a model that mimics breast cancer metastasis. Today, 90% of breast cancer (BC) death is cased be metastasis. This is largely because we are still unable to understand the mechanisms of metastatic progression. Consequently, we are unable to drug and treat to cure metastatic disease. Better models of cancer metastasis will lead to more fundamental insights. Drug evaluation using this model will enable clinicians to make more rational decisions for drug efficiency. In our project, we will reconstruct the primary breast tumor and metastatic target organs such as liver, lung and bone (the most common clinical breast cancer metastasis organs). We will do so by creating small (<200um) cellular building blocks, containing the most important cell types of the BC and the healthy target organs. Next, we will use a 3D bioprinter which enables us to precisely design and print 3 dimensional tissue constructs with different sizes and shapes. In a last critical step we bring the 3D BC construct and the 3D lung, liver and bone construct in perfusion system. This perfusion system mimics the blood circulation. Finally, in this model we can observe and investigate in vitro metastatic progression which can elucidate the metastasis process and help to develop and evaluate more effective drugs.