Interaction of the human body with electromagnetic fields is widely used in medical devices for both diagnosis and therapeutic purposes. Over the last decades there has been a continuous trend to replace X-ray-based devices in favor of EM-based ones. Additionally, wireless communication of implanted devices is gaining importance. The main challenge during the development of such devices, is the detailed understanding of the field distribution inside the body, since measurement inside living organisms is almost impossible. Here, simulation can be of great benefit. In this webinar we show that human body models have evolved to the point where both the electromagnetic radiation effects as well as macroscopic effects, such as heating, Specific Absorption Rate (SAR) distribution, etc. can be predicted with tools provided by CST®. Through the appropriate selection of a body model, it is possible to personalize medical treatment plans and greatly improve diagnosis tools without the need for excessive invasive testing. Using several examples, we will show the toolbox of features related to biomedical simulations which are available to the user of CST STUDIO SUITE®. These include the calculation of field distributions inside and the power absorbed by the body and thermal effects due to these fields.