Miniaturized microtools based on recent nano/micromachining technology increase its importance in nanoscale science and nanoengineering. We have developed various micro/nano probes for nanometric sensing and processing. A silicon probe array with integrated electrostatic actuators could manipulate an individual nanomaterial and characterize its electric properties. Irradiation of a laser beam on the small gap of the two metallized probes with the electrostatic actuator generates a localized near-field light beyond the diffraction limit of light with a high efficiency because of surface plasmon enhancement, and scanning optical near-filed microscopy (NSOM) was demonstrated. In order to overcome its low wear resistance on these silicon probes, diamond microfabrication was developed. A diamond multiprobe with an integrated diamond tip on each probe could applied to thermomechanical lithography for defining features of 20 nm, and also high-density data storage based on ferroelectric nonlinear scanning microscopy was demonstrated. Miniaturization of mechanical sensing elements enables to raise its resolution and response. In order to integrate individual carbon nanotube (CNT) into these probes, a selective growth technique using field-enhanced chemical vapor deposition (CVD) was de developed. Nanofabrication of single crystalline silicon for nanomechanical sensing was developed and minimum thickness of 20 nm was achieved. Ultrathin single crystalline silicon cantilevers with a thickness of below 100 nm exhibit a very low thermomechanical noise, and applied to ultra-high sensitive sensing for a small force and mass. A force of below 3.0×10-16 N was detected in vacuum at room temperature, which will open up new applications in imaging science. Using the developed mass sensors, a minimum detectable mass of 10-18 g in vacuum and 2×10-14 g in atmosphere were demonstrated for bio-chemical sensing. This nanomechanical structure has a limitation in the detectable minimum value in atmosphere because of the low Q factor originated in gas dumping. Therefore, we have been studying resonant structure of AT-cut quart that has shear vibration mode with a feasibility of high Q factor in atmosphere. A resonator made of the AT-cut quartz with a cantilevered shape shows various vibration modes depending on the excitation frequency, and high sensitive force and chemical sensing are expected. We believe that instrumentations developed by NEMS/MEMS will play an important role in future nanoscience and nanoengineering.