In the late 1980s, micromachine technology emerged by applying the integrated circuit (IC) manufacturing processes to fabricate mechanical parts with feature sizes in the order of microns. This approach opens new domains both for fundamental research and for applications in all engineering disciplines. The surface to volume ratio of a device is inversely proportional to its length scale. In the case of a micron range length scale, the large surface to volume ratio accentuates the surface effect. We might need to include the originally discarded surface forces and re-examine the constitutive relation as well as the boundary condition in the mass, momentum transport equations. For example, the viscosity of a simple fluid can be a function of the device size. We have also become aware that the thermal conductivity of thin-layered material can only be 1% to 10 % of the bulk material value depending on the size of the layer and its surface roughness. During the last decade, large varieties of microsensors and microactuators have been developed based on the micromachine technology. These microtransducers can be integrated with an IC based logic circuit to form a micro-electro-mechanical-system (MEMS) which is able to perform sensing-decision-actuation functions. This capability enables us to control natural phenomena in real-time and/or in a distributed manner. The MEMS controlled phenomena under investigation ranges from maneuvering an aircraft with a size of meters to detecting DNA with a size of a nano meter.