The first part of the course is dedicated to a simulation code which transports neutrons, photons and electrons, as well as charged particles. There will be a series of practical lessons, after a brief theoretical introduction, in which the students will learn to create an input file and to simulate transport problems. At the end of this first part, the students will be able to create geometries, to set the physics, to make requests to the program and to analyze the results from a statistical point of view. The second part of the course is dedicated to the modelization and simulation of radiation-induced biological effects at the sub-cellular/cellular level and at the level of tissues and organs. The attention will be focused on chromosome aberrations and their consequences in terms of cell death or cell conversion to malignancy, as well as the modelization of such effects at the tissue/organ level, with examples of applications in hadrontherapy and space radiation protection.