Units of radiation dose to biological organisms are introduced and demystified (there are many, but they are all related). Methods of measuring dose are introduced, as well as measuring dose by different types of radiation. The difference between dose (energy absorbed per unit mass) and damage (dose times effectiveness of radiation at causing cellular defects) is specifically introduced. Ways of using ionizing radiation for medical treatment (brachytherapy, diagnostics, x-ray and proton cancer therapy) are explained from a physical point of view. Prof. Short explains how his uncle very intelligently used principles of ionizing radiation and mass attenuation to smuggle diamonds out from Apartheid South Africa.