This paper covers the investigation of the microscale behavior of Pt nanostrucures fabricated by atomic layer deposition (ALD) at elevated temperature. Nanoparticles are fabricated at up to 70 ALD cycles, while congruent porous nanostructures are observed at > 90 ALD cycles. The areal density of the ALD Pt nanostructure on top of the SiO2 substrate was as high as 98% even after annealing at 450℃ for 1hr. The sheet resistance of the ALD Pt nanostructure dramatically increased when the areal density of the nanostructure decreased below 85 - 89% due to coarsening at elevated temperature.