The morphologies and surface dynamic processes on RuO2 single-crystal substrates were studied using scanning tunneling microscopy (STM) under non-vacuum conditions. The as-grown oxide surfaces show a variety of constructs and aggregations of a-top atoms that form secondary microstructures with no distinct periodicity. Atomically resolved images captured on adjacent terraces of the same sample indicate differences in a-top atomic arrangements on a single-crystal surface. After annealing an as-grown sample in air at similar to 450 degreesC for 2 h. the STM images show an ordered, long-range surface reconstruction along the c-axis of the crystal lattice. Combined. this morphological diversity and structural rearrangement suggest motion and clustering of the surface atoms at elevated temperatures.