As a physicist, Harald Hess developed low temperature scanning probe microscopes to visualize diverse physics phenomenon at Bell Labs. After 1997 he developed equipment for hard disk drive and semiconductor inspection and production. In 2005 he and a colleague, Eric Betzig, invented a high resolution microscope, PALM, for cell biology. PALM was built in a La Jolla condo, tested at the National Institute of Health and extended to 3D at Janelia/HHMI where he presently works. He is also developing 3D electron microscopy techniques for volume imaging of cells and neural tissue and exploring how they can be combined with PALM.