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	What is cosmic ray? Cosmic rays are nuclei and elementary particles always falling very fast on the earth from the universe. Enormous number of cosmic rays are passing through our bodies. Galactic cosmic rays are expected to arrive at the earth after traveling about 10 million years. They plunge into the atmosphere and bring about nuclear reactions with nuclei of oxygen and nitrogen in the air. The extraterrestrial cosmic rays which come from outside the earth are conventionally called primary cosmic rays, and newly produced paricles via the nuclear reactions are called secondary cosmic rays. What will turn out by studying cosmic rays? Why we study cosmic rays is that a lot of information, for instance on the origin of force working between substances and on the structure of universe, are hidden there. The former Minister of Education, Akito Arima, gave the following word to the Kamioka group of this institute: "The cosmic ray is a heavenly revelation." This word shows the essence of the cosmic ray. The cosmic ray is exactly a sign sent from the heaven, in which information on a wide range of problems from the micro-world connected with the root of substance to the macro-world of the universe is packed. Speaking historically, the elementary particle physics itself was born from the observation of cosmic rays. For quite a while after that, studies of elementary particles have been carried out mainly using artificial accelerators, but recently much hope is focused again on new observations of cosmic rays using large fully high-tech detectors. This institute, as the unique institute in the world devoted only to the cosmic ray, keeps researches to repond to such hope. How to investigate cosmic rays? There are various ways of investigating cosmic rays depending on the object of the invesgation. To investigate the primay cosmic rays directly, we have to go to as high altitude as possible. We go to high mountains, launch baloons, etc. When an ultra-high energy primary cosmic ray enter the atmosphere, electrons, gamma rays and muons in the secondary particles fall on a wide area of the surface like a shower. We call such a phenomenon an air shower. To investigate the air shower in a specified way, we sometimes go to a wide basin with clean air. As it is difficult to select neutrinos and high energy muons in the other background cosmic rays, we go to the undergroud where the background can not reach. The researches in this institute cover all those species of cosmic rays mentioned so far. In this institute, the gravitational wave possibly coming from the universe is included in the research projects. The gravitational wave is the distortion of space propagating in the universe with the velocity of light, which is caused when a massive object is put into motion. This is one of the problems not verified yet among the Einstein's predictions. To find very small distortions of space, we maximize the detector sensitivity. Therfore the experiment is done at a very calm place without trembles and vibrations. By adding the study of the gravitational wave, the most uninvestigated elementary particle, graviton, will be lighted up, and the clarification of the mysteries of substance and universe will be much progressed.