In this opening chapter, I will establish the foundation for the upcoming discussion by first covering fundamental information. This includes key terminology, the classification of psychedelics, the primary agents involved, and their natural sources. Then, I will explore the historical and contemporary landscape of psychedelic use, tracing its origins in ancient rituals and examining its resurgence in modern research. I will provide a timeline of key events in psychedelic research, highlighting the cyclical nature of scientific and societal interest in psychedelics, including periods of both prohibition and renewed exploration, referred to as the “psychedelic renaissance.” Next, I will introduce the concept of “set and setting,” emphasizing the significant influence of contextual factors on the psychedelic experience. I will close by clarifying the distinction between “spiritual” and “religious” experiences, providing a framework for interpreting the subjective effects often associated with psychedelic use. By analyzing fundamental information and historical context, this chapter lays the groundwork for the subsequent comprehensive exploration of psychedelics and their role in human religious practices.