Based on a novel approach to single molecule imaging, our team has pioneered the application of single-molecule studies to immunology. The goal of single-molecule immunoimaging is to visualize immunological responses and signaling processes at the single-molecule level and within single cells. To this end, a new type of fluorescence microscopy, termed “Highly Inclined and Laminated Optical Sheet” (HILO) microscopy, was developed. A microscope system was installed at RCAI and various collaborations with different groups at the center have been initiated. Our group has focused on the development of novel types of fluorescence microscopy for use in single cell/single molecule studies. In addition, we are developing analysis software tools for imaging and quantitative analysis. Presently, more than eight external research collaborations including international collaborations are ongoing.