1. A method of investigating a flux of output electrons emanating from a sample in a charged-particle microscope, which flux is produced in response to irradiation of the sample by a beam of input charged particles, the method comprising the following steps: using a detector to intercept at least a portion of the flux so as to produce a set {I j } of pixeled images I j of at least part of the sample, whereby the cardinality of the set {I j } is M>1; for each pixel pi in each image I j , determining the accumulated signal strength Sij, thus producing an associated set of signal strengths {S ij }; using the set {S ij } to calculate the following values: an average signal strength S per pixel position i; a variance σ 2 S in S per pixel position i; using these values S and σ 2 S to produce at least one map of said part of the sample, selected from the group comprising: a first map, representing variation in energy of detected electrons as a function of position, and; a second map, representing variation in number of detected electrons as a function of position.