In this seminar I will show the approach we have developed to study the interactions between cytotoxic T cells and cancer spheroids in microfluidic droplets. I will describe the original technical approach, as well as the initial measurements using mouse cells. I will end by describing our ongoing work where we use human patient-derived cells. I will pay particular attention on the analysis of the spatio-temporal data to decipher cell-cell interactions with increasing complexity of the cancer and immune models.