The in vivo Bioluminescence, Epi-Fluorescence, and Trans-Fluorescence imaging system (OiS300) is a pivotal tool in biomedical research, particularly for studies involving mice and other small animals. Its advanced features include exceptional sensitivity and customization options, such as adjustable excitation and emission filters, which enhance its versatility for various imaging applications. The system employs an EMCCD camera capable of photon counting, ensuring highly sensitive detection of weak bioluminescent and fluorescent signals. Additionally, the OiS300 supports 3D visualization, allowing researchers to obtain detailed spatial information about biological processes in living organisms. This combination of high sensitivity, flexibility, and advanced imaging capabilities makes the OiS300 an invaluable asset for in vivo biomedical research.