Single-molecule and particle detection on true portable microscopy platforms

•There is a global need for low-cost, point-of-care tools for single-molecule analysis.•True portable devices for single-molecule and particle detection are reviewed.•3D-printed and smartphone-based platforms represent low-cost routes to portable microscopy.•Fluorescence, holography, and plasmonic-enhanced methods are prominent.•Outlooks and perspectives on potential directions for the field are offered.