Immunotherapies represent a powerful suite of treatments that co-opt the immune system to target deleterious cellular conditions. They have been effective with a series of cancers and other disorders. The problem is that development of new antibodies can be challenging for several technical reasons, but also because no two people are alike. Dr. Liang Schweizer of HiFiBio describes how her company is using single-cells and microfluidics to identify new antibodies that may be mobilized against discrete cellular targets, as well as what they have learned about heterogeneity between patients and how to identify specific biomarkers that could guide application of the most effective treatments.