Separating complex mixtures of cells, such as those found in a blood sample, can offer valuable information for diagnosing and treating disease. However, it may be necessary to search through billions of other cells to collect rare cells such as tumor cells, stem cells or fetal cells. Researchers have now demonstrated a new microfluidic device that can isolate target cells much faster than existing devices. Such technology could be used in applications such as point-of-care diagnostics and personalized medicine.