Quantum dots are nanometer-scale semiconductor particles with exquisite optical and electronic properties characterized by quantum confinement. These nanocrystals associated with cadmium selenide and indium phosphide materials have had a considerable impact on many disciplines, especially in the biomedical sciences. Since their conceptualization in the early 1980s, many breakthroughs in their synthesis, surface modification, and functionalization have pushed their application in diagnostics, imaging, and therapeutics. This chapter reviews in detail the historical evolution, synthesis methods, and modes of characterization of QDs, with a focus on biomedical applications. Owing to their unique optical properties, size-tunable emission, and high photostability, QDs are recommended for fluorescence imaging and multimodal imaging systems. On the other hand, QD-based biosensors and targeted drug delivery systems are highly promising for applications in the emerging field of precision medicine. Although QDs hold much promise, their cytotoxicity and biocompatibility have been major concerns. Hence, in-depth research studies and new strategies are needed so that these materials can be devoid of fatal side effects. Strict ethical considerations and regulatory frameworks also play crucial roles in the clinical translation of these biomarkers. Assuming that further research progresses, integration with other nanotechnologies or improvement of QD design can be more likely to lead to enhancements in efficacy and safety, thus indicating a transformative influence on both personalized medicine and nanomedicine. This chapter concludes with the future prospects and challenges to be addressed in the full realization of potential for QDs in the biomedical field.