Rare phenomena are often connected with the physics beyond the standard model of particle physics. Experimental investigation of such phenomena should be pursued in a very low background environment and consequently underground sites are often chosen. Dark matter search and search for neutrino-less double-beta-decay are the most active fields in this context. For a high sensitivity search, various features are implemented in those experiments. Very common feature is low radioactive impurity. Very low energy threshold, very high energy resolution, particle identification and track information are also required in various realizations. Thus, varieties of detector techniques are employed. As sensitivity improves, target mass and scalability are becoming more and more important. How to accommodate growing detector in a common shielding system is a major concern. I will introduce typical detector technologies and some detector realizations from these aspects.