It is very hard work to develop detectors, but it finally leads us to an exciting world. Together with a hand-picked group of colleagues, I have been working on the development of high-sensitivity hard X-ray and gamma-ray detectors for high-energy astrophysics. We also tried to apply our system to the visualization of radioactive substances and demonstrated its performance in Fukushima. For the last two years in Okinawa, I have been enjoying conducting research and development for small animal imaging with a capability of high-resolution tracking of radioactive probes. Here at Kavli IPMU, I will try to address the complexity of tumors in a living body with the power of hard X-ray and gamma-ray imaging. The first prototype is now ready in the Kashiwa Research Complex 2 building. Welcome!