It is clear that the behaviour of tumours cannot be ascribed solely to cancer cell-autonomous traits. The tumour environment is composed of multiple cell types, only a proportion of which are cancer cells. In this session we will consider the recruitment, activation and role of Cancer Associated Fibroblasts, T cells and macrophages in the tumour environment, particularly exploring the factors that control their modulation of cancer cell migration, metastasis and therapeutic responses. The use of techniques such as RNAi-based screening, parallel sequencing, biological co-culture and fluorescence-based intra-vital imaging through optical windows will be described, as we strive to better understand tumour-host interplay in cancer progression and how this might be modulated for therapeutic benefit.