Ideally, evidence destruction (which is also occurring when the document analysis is carried out using the commonly accepted TLC-based technique) should be avoided, and the continuous advances in using MS instrumentation as imaging tools may allow this goal to be achieved (at least for documents of modest size). The small-scale nondestructive LDI MS analyses were carried out in this work using the imaging capability of modern state-of-the-art MALDI TOF mass spectrometers. While such instrumentation remains relatively expensive and is unlikely to become a part of the experimental arsenal of teaching laboratories any time soon, many academic mass spectrometry facilities do have imaging MALDI MS, which might be used for advanced projects by undergraduate chemistry majors. A variety of experiments could be implemented as a follow-up to the work presented in the previous sections. For example, Figure illustrates how alteration of hand-written documents can be detected by producing molecular images of the surface of a piece of paper with questionable writing ("8" had been added right before "100" imitating the handwriting style and using the pen with the ink indistinguishable from that used for the original writing). The chemical image of the surface was produced by rastering the sample under the stationary laser beam, such that a mass spectrum was acquired for every pixel. The resulting data array was converted to a two-dimensional signal intensity map of ions at m/z 358 representing one of the most abundant dyes, methyl violet B (structure (1) in Figure ). The dramatic signal intensity mismatch in Figure provides a clear indication that the abundance of methyl violet B is significantly higher in the first handwritten number compared to the rest of the entry, proving that different inks were used to enter "8" and "100." Since a complete mass spectrum is acquired for each pixel in chemical imaging experiments, the students can extract multiple maps (representing different dyes) from a single data set. Superposition of such intensity maps can be used to establish the chronological order for overlapping entries where visual inspection alone is not sufficient, e.g. to reveal "signature over print" vs. "print over signature" orders in disputed signed documents, where the order of placing the entries is uncertain and cannot be determined by visual inspection (similar to the case shown in Figure , where the "legitimate" text should be below the layer of pen ink at all intersections, while all added text will be inevitably placed over the pen strokes of the signature). An example of such analysis is presented in Figure , where a text was printed over handwriting, and this order is readily established by observing the ionic trace at m/z 1209 (representing PEG molecule unique for the printer ink) overlaid on top of the ionic trace for m/z 358 (representing methyl violet B, an ink dye not present in the printer ink).