Optical imaging is becoming a versatile tool in the fields of life science and biomedical research. Various conventional and advanced optical imaging techniques are used in research, where label and label-free imaging techniques are very important. However, most biological samples are transparent, and label-free images provide low contrast. Therefore, in such cases, samples must be tagged with exogenous fluorophores, which will provide better contrast and additional morphological information. As we consider labelled imaging, fluorescent probes such as organic dyes provide lower photostability and brightness along with a limited range of emission spectra. As alternative fluorescent probes, quantum dots (QDs), which have wide emission spectra and high photostability, are being used in bioimaging. This chapter highlights the various optical properties of fluorescent probes by comparing the advantages of QDs over other fluorescent probes, such as organic dyes. Because of their unique optical properties, such as tunable particle sizes with sharp emission spectra, high quantum yields and photostability. Quantum dots (QDs) are becoming prominent fluorescent probes in optical imaging. The current chapter discusses the role of different QDs in enhancing the sensitivity and resolution of imaging techniques, providing more specific molecular and cellular analysis by using advanced optical imaging techniques such as widefield microscopy, confocal microscopy, Förster resonance energy transfer (FRET), fluorescence lifetime imaging microscopy (FLIM), fluorescence recovery after photobleaching (FRAP), and two-photon microscopy (TPM), along with the principles behind the imaging technique. By referring to several studies and recent discoveries in advanced imaging techniques, this chapter provides a summary of the revolutionary role of QDs in optical imaging, offering innovative insights into biomedical research.