This paper describes concept of subsurface micro-sensing. It is intended to achieve an epoch-making development of subsurface engineerings by developing such technologies as micro measurement of well interior, micro measurement while drilling (MWD), and micro intelligent logging. These technologies are supported by development of micro sensors and micro drilling techniques using micro machine technologies. Micronizing the subsurface sensors makes mass production of sensors with equivalent performance possible, and the production cost can be reduced largely. The sensors can be embedded or used disposably, resulting in increased mobility in measurement and higher performance. Installing multiple number of sensors makes high-accuracy measurement possible, such as array measurement. The sensors can be linked easily with photo-electronics components, realizing remote measurement at low price and high accuracy. Control in micro-drilling and MWD also become possible. Such advantages may also be expected as installing the sensors on the outer side of wells in use and monitoring subsurface information during production. Expectation on them is large as a new paradigm of underground exploration and measurement. 1 fig.