Three dimensional fiducial

A method and system for forming and using a fiducial on a sample to locate an area of interest on the sample, the method comprising forming a fiducial by depositing a block of material on a sample proximal to an area of interest on the sample, the block of material extending from the surface of the sample to a detectable extent above the surface of the sample; and milling, using a charged particle beam, a predetermined pattern into at least two exposed faces of the block of material; subsequent to forming the fiducial, detecting the location of the area of interest by detecting the location of the fiducial; and subsequent to detecting the location of the area of interest, imaging or milling the area of interest with a charged particle beam.