Primary purpose of this lecture is to present on Radiation and Radioactivity: Units and Quantities. Here briefly focus on Quantities (mass, volume, time, etc.) vs. Units (grams, gallons, hours) and Units of exposure, radioactivity, and energy associated with ionizing radioactivity. Radiation studies began in 1895 with the discovery of x-rays. Early physicist and therapist eventually knew that ionizing radiation was hazardous, however, there was no definite way to quantify the dose or damage. No suitable unit.