The ultimate aim of radiobiological research is to establish a quantitative relationship between the radiation dose absorbed by biological samples (being this a cell, a tissue, an organ, or a body) and the effect caused. Therefore, radiobiological investigations need to be supported by accurate and precise dosimetric measurements. A rigorous standardized methodology has been established to assess and quantify the radiation dose absorbed by biological samples and these will be reviewed and discussed in this chapter. Dosimetric concepts at the macro- and microscopic levels are discussed with a focus on key physical quantities, their measurement technologies, and the link to the biological damage and response. This chapter will also include a description of state-of-the-art irradiation facilities (e.g., mini- and micro-beams) used for probing mechanisms underpinning radiobiological responses. Finally, the link between energy deposition events and detectable biological effects (from the molecular to the organism level) is investigated using Monte Carlo simulation codes and macroscopic radiobiological models.