This paper presents the 2 omega method, a newly developed ac mode local thermal property imaging technique with nanoscale spatial resolution. The authors batch-fabricate the thermoelectric probe, whose junction size is about 200 nm, with yield higher than 95%. The shortest time constant of the thermoelectric probe is measured to be 0.72 ms.. They experimentally demonstrate that the 2 omega method can map out the local thermal property of a sample by monitoring the amplitude of the 2 omega signal from the thermocouple junction of a probe heated by an ac. By comparing with the thermal property images obtained by other methods, they also show that the 2 omega method using the point-heating and point-sensing scheme is the most suitable for the nanoscale thermal property imaging. (c) 2006 American Vacuum Society.