This chapter presents an extensive investigation into the diverse landscape of in vitro models tailored for unraveling the complexities of tumors. The exploration unfolds with a meticulous examination of two-dimensional (2D) tumor models in Sect. 2, providing a comprehensive understanding of their distinct characteristics and inherent limitations. The narrative then seamlessly transitions to Sect. 3, where the focus broadens to encompass three-dimensional (3D) models, exploring the realms of spheroids, organoids, and ex vivo explant models (Sects. 3.1, 3.2, and 3.3). The chapter delves into the frontier of bioprinting in Sect. 3.4, elucidating its applications and addressing challenges associated with this cutting-edge technology. Section 3.5 investigates the pivotal role of microfluidics in cancer research, underscoring its contributions to mimicking the tumor microenvironment. The exploration culminates in Sect. 3.6, dedicated to models involving the chorioallantoic membrane, shedding light on their unique attributes and significant contributions to cancer studies. This comprehensive overview aims to elevate our comprehension of the current spectrum of in vitro tumor models. By delineating the nuanced characteristics of each model type, the chapter provides valuable insights that are poised to influence the methodologies of future cancer research. Emphasizing the collective impact of these models on advancing preclinical studies, this chapter serves as a foundational resource, fostering innovation and informed decision-making for the development of more effective therapeutic strategies in cancer treatment.