This is an 8-part lecture series on the Danger Model presented at the National Institutes of Health to 198 invited scientists. Danger is the most routinely predictive of the models proposed to explain how the immune system functions. Dr Matzinger illuminates the field of immunology with ironic insights and uncanny clarity of vision. Her lecture on tumors (#3 below) is perhaps the most important message in her entire oeuvre. It has certainly changed our minds.