In Model Driven Engineering (MDE), models are first-class citizens, and model transformation is MDE's "heart and soul". Since model transformations are executed for a family of (conforming) models, their validity becomes a crucial issue. This paper proposes to explore the question of the formal verification of model transformation properties through a tridimensional approach: the transformation involved, the properties of interest addressed, and the formal verification techniques used to establish the properties. This work is intended for a double audience. For newcomers, it provides a tutorial introduction to the field of formal verification of model transformations. For readers more familiar with formal methods and model transformations, it proposes a literature review (although not systematic) of the contributions of the field. Overall, this work allows to better understand the evolution, trends and current practice in the domain of model transformation verification. This work opens an interesting research line for building an engineering of model transformation verification guided by the notion of model transformation intent.