This tutorial presents the holistic modeling concept in the context of metal-oxide-semiconductor field-effect-transistors (MOSFETs). First, the standard MOSFET modeling approaches will be comparatively discussed. Subsequently, several factors impacting the operation of MOSFETs will be explained in terms of their physical origins and their modeling, as already undertaken in the literature. These factors include process variations, time-based degradation, as well as extreme environmental conditions, such as low or high temperatures and ionizing radiation. Subsequently, the need for considering these phenomena in joint configurations is demonstrated through experimental data. Finally, an implementation strategy for holistic modeling will be proposed by introducing 'extreme corners', which represent the combinations of conventional process corners with the mentioned factors at various values of interest.