The overall goal of the fellowship is to gain a better understanding how tumour associated macrophages (TAMs) contribute to the intravasation of cancer cells, an essential step in metastasis. The key goals of this project are to: 1) Investigate the origin, location and flexibility in function of different TAM subsets, including the metastasis-assisting macrophages 2) Determine how breast (cancer) cells and fibroblasts are influencing macrophages during tissue development and metastasis. I will explore where these metastasis-assisting macrophages (MAMs) are coming from and what the influences of cancer cells and fibroblast are on the differentiation of normal macrophages into MAMs. I will apply intravital imaging with mammary-imaging windows and photo-switching technology to mouse models of breast cancer to improve understanding of microenvironment involvement in tumour metastasis. This will be a joint project with Prof. Condeelis (USA) and Dr. Sahai (UK).