The article reviews the development and applications of lanthanide probes for optical imaging, focusing on two main classes: luminescent and magnetic lanthanides. Lanthanide probes are particularly attractive for optical imaging due to their long luminescence lifetimes, which enhance signal-to-noise ratios and improve sensitivity. The review discusses the design and photophysical properties of luminescent lanthanide probes, including the role of the metal center, chelates, and sensitizing antennae. It also explores how these components are tuned to develop bioresponsive probes for optical imaging. Additionally, the article covers the principles of circularly polarized luminescence (CPL) and its applications in biological sensing. The section on bioresponsive modulation of lanthanide luminescence highlights methods to alter the probe's photophysical behavior in response to biological stimuli, such as pH changes, anion binding, and enzyme activity. The review concludes with examples of successful applications of these probes in both bioassays and cellular imaging, emphasizing their potential for quantitative analysis and dynamic cellular process detection.The article reviews the development and applications of lanthanide probes for optical imaging, focusing on two main classes: luminescent and magnetic lanthanides. Lanthanide probes are particularly attractive for optical imaging due to their long luminescence lifetimes, which enhance signal-to-noise ratios and improve sensitivity. The review discusses the design and photophysical properties of luminescent lanthanide probes, including the role of the metal center, chelates, and sensitizing antennae. It also explores how these components are tuned to develop bioresponsive probes for optical imaging. Additionally, the article covers the principles of circularly polarized luminescence (CPL) and its applications in biological sensing. The section on bioresponsive modulation of lanthanide luminescence highlights methods to alter the probe's photophysical behavior in response to biological stimuli, such as pH changes, anion binding, and enzyme activity. The review concludes with examples of successful applications of these probes in both bioassays and cellular imaging, emphasizing their potential for quantitative analysis and dynamic cellular process detection.