Deposition of microdroplets is fundamental to many emerging technologies. The strongly coupled droplet spreading and cooling processes have profound impact on the quality of droplet-formed structures. This work developed a microsensor for characterizing rapidly spreading microdroplets on a substrate after the impact. The sensor consists of fine conducting lines made of Au and Ti two-layered structure with both width and spacing 2 μm. Transient droplet contact diameters were measured with the sensors of 8 μm spatial and 1 μs temporal resolutions. Two different regimes of spreading were discovered: an extremely fast initial spreading process followed by slow spreading. The results are important for achieving a better understanding of rapid solidification and formation of novel microstructures in droplet-based manufacturing processes.