Every day our bodies are being attacked by foreign organisms including bacteria, viruses and parasites that can cause disease, and our immune system has evolved into a complex defence network of cells and chemicals. Our understanding of how the immune system works both for and against our health gets better with every passing year. Technical advances in cell biology tools, such as flow cytometry and high-content imaging, and genomics tools, such as long-read DNA sequencing and single-cell isolation and characterisation, continually add to our understanding of all disciplines of immunology: classical, developmental, clinical, immunotherapy and immuno-oncology.