The present invention is a method to determine where fractures are created within a wellbore during a formation fracturing operation, the method comprising the steps of: providing at least one sensor within a carrier capable of measuring and recording a pressure difference across the carrier as a function of time; releasing the sensor into fracturing fluids; injecting fracturing fluids into a wellbore during a fracturing operation; after at least one fracture has formed, permitting fluids to flow back from the fractured formation into the wellbore and to a surface facility; capturing at least one sensor from the fluids which flowed back from the fractured formation; reading recorded data from the captured sensor; and determining the relative size of at least two different fractures based on the recorded data.