A number of rock samples has been collected by the Japanese Decoding Earth Evolution Program (DEEP) aiming to decode early history of life and the Earth. It is necessary to have working hypothses on the relationship between evolution of life and Earth's environments, in order to relate possible ecological events and geological informations to have been recorded in the rock specimens. Interdisciplinary studies of microbial mats occurring at hotsprings has been started to get newer views of Precambrian biospheric evolution.