This chapter describes small and large preclinical animal models of disease, focusing on cardiovascular, cancer, and neurodegenerative pathologies, since they represent the most important leading causes of prevalence and death; therefore, they constitute a very significant piece of extensive investigation from the bench to bedside. The use of preclinical animal models in biomedical research is a key step in elucidating the plethora of host signals triggered in response to pathogenesis and implies a significant advancement in the evaluation and improvement of procedures focused on early diagnosis, progression of disease, and the evaluation of novel therapeutic approaches. Animal models serve as valuable and powerful tools in preclinical investigation toward a common horizon focused on translational medicine. Thanks to the latest technological advances, today it is feasible to recreate any human pathological condition in different animal templates. In combination with the newest advances in non-invasive molecular imaging technologies, fascinating upcoming events are yet to come.