A new type of super-resolution optical microscopy that uses a trio of laser beams to display very small particles at below the diffraction limit, or half the width of the wavelength of light. Unlike conventional optical microscopes that can only resolve objects no smaller than about 300 nanometers, or billionths of a meter, STAM breaks the diffraction limit that has been viewed as the fundamental limit of optical imaging resolution. STAM allows researchers to view molecules such as proteins and lipids, as well as synthetic nanostructures like nanotubes, which are a few nanometers in diameter.

STAM uses a laser beam that selectively illuminates some molecules but not others. Electrons in the atoms of illuminated molecules are excited temporarily into a higher energy level, while the others remain in their ground state. Images are generated using a laser called a probe to compare the contrast between the excited and ground-state molecules.

The super-resolution optical microscopy opens new windows into the nanoscopic world, bringing advances in a diverse range of disciplines, from medicine to nanoelectronics.