An apparatus for thinning at least part of a sample into a wedge for electron microscopy, said sample having a leading edge for the wedge, a tailing edge for the wedge and an axis in a lateral direction extending therebetween and said apparatus having an ion beam generator which is configured to emit an ion beam directed at a target area on the surface of said sample to thin the at least part of the sample by removing material from said target area of said sample, wherein said apparatus comprises: (i) an electron beam generator which is configured to emit an electron beam which is configured to scan the electron beam across said target area in a direction along said axis; and (ii) an electron beam detector mounted opposite said electron beam generator with respect to said sample and in electronic communication with said ion beam generator, said electron beam detector is configured to: (a) receive electrons from said electron beam when said electrons meet at least one of the conditions of: passing through, deflected by and passing adjacent sample material within said target area; and (b) generate a first electronic signal resulting from measurement: associated with a plurality of locations along said axis; and indicative of a quantum of electrons received by said electron beam detector meeting at least one of the conditions of: passing through, deflected by and passing adjacent said target area, taken along said axis, wherein the first electronic signal corresponds to a line in a graph, showing a percentage of electrons passing through said target area as a function of the plurality of locations along the axis, and indicates a degree to which said ion beam has removed material from said target area; and (iii) a processor in electronic communication with said ion beam generator and said electron beam detector, said processor configured to transmit a second electronic signal to said ion beam generator to cause the termination of said generation of said ion beam when said first electronic signal corresponding to the line (200, 201, 201A, 202) exhibits a continuous and even slope in a range for the plurality of locations along the axis beginning at the tailing edge and ending at the leading edge, and in a range for the percentage of electrons passing through said target area beginning at 0% and ending at 100%. (i) an electron beam generator which is configured to emit an electron beam which is configured to scan the electron beam across said target area in a direction along said axis; and (ii) an electron beam detector mounted opposite said electron beam generator with respect to said sample and in electronic communication with said ion beam generator, said electron beam detector is configured to: (a) receive electrons from said electron beam when said electrons meet at least one of the conditions of: passing through, deflected by and passing adjacent sample material within said target area; and (b) generate a first electronic signal resulting from measurement: associated with a plurality of locations along said axis; and indicative of a quantum of electrons received by said electron beam detector meeting at least one of the conditions of: passing through, deflected by and passing adjacent said target area, taken along said axis, wherein the first electronic signal corresponds to a line in a graph, showing a percentage of electrons passing through said target area as a function of the plurality of locations along the axis, and indicates a degree to which said ion beam has removed material from said target area; and (a) receive electrons from said electron beam when said electrons meet at least one of the conditions of: passing through, deflected by and passing adjacent sample material within said target area; and (b) generate a first electronic signal resulting from measurement: associated with a plurality of locations along said axis; and indicative of a quantum of electrons received by said electron beam detector meeting at least one of the conditions of: passing through, deflected by and passing adjacent said target area, taken along said axis, wherein the first electronic signal corresponds to a line in a graph, showing a percentage of electrons passing through said target area as a function of the plurality of locations along the axis, and indicates a degree to which said ion beam has removed material from said target area; and associated with a plurality of locations along said axis; and indicative of a quantum of electrons received by said electron beam detector meeting at least one of the conditions of: passing through, deflected by and passing adjacent said target area, taken along said axis, wherein the first electronic signal corresponds to a line in a graph, showing a percentage of electrons passing through said target area as a function of the plurality of locations along the axis, and indicates a degree to which said ion beam has removed material from said target area; and (iii) a processor in electronic communication with said ion beam generator and said electron beam detector, said processor configured to transmit a second electronic signal to said ion beam generator to cause the termination of said generation of said ion beam when said first electronic signal corresponding to the line (200, 201, 201A, 202) exhibits a continuous and even slope in a range for the plurality of locations along the axis beginning at the tailing edge and ending at the leading edge, and in a range for the percentage of electrons passing through said target area beginning at 0% and ending at 100%.