This book is based on a doctoral thesis submitted to the University of Bern in thesummerof2002. Researchonthethesiswasmadepossiblethroughagrant provided by the Swiss National Science Foundation (SNF) from 2000 to 2002 foraprojectonthehistoryandepistemologyofscienti?cillustrations(Project No. 1152-059499). Gerd Graßho? headed this programme at the University of Bern and made my reworking of the thesis into a book in English possible. He also provided the funding for the services of a professional copy editor (Margareta Simons, Bern). The?ndingspresentedinthisbookarecloselyrelatedtothegeneralresults of the SNF project, which are published elsewhere: the source material can be 1 consultedinanearliermonographandinanelectroniceditionontheinternet; thetheoreticalapproachwillbemorethoroughlyinvestigatedinatextbookon the analysis of scienti?c illustrations. In addition, this study has made use of theoretical concepts developed by Gerd Graßho?, which, in their latest form, have yet to be published; these concern primarily the model concept discussed in Chapter 3. The criteria put forward for optimizing scienti?c illustrations, which are dealt with in Chapter 7, were also originally proposed by Gerd Graßho?; they were re?ned and elaborated in the SNF project. Some of the material on the copying links presented in this book was ?rst published in 2 an article in Studies in History and Philosophy of Science; Part C; while some of the material in Chapter 5 on the hand-colouring of illustration was 3 published prior to this book in the Annals of Science. Iwasabletoaccesssourcematerialforthisstudyfromseveralarchivesand 4 institutions. Most of the images that I examined originated from copies held in the University Library Göttingen, while the remainingillustrations came 1 See Nickelsen (2000), Nickelsen & Graßho? (2001) and Graßho? et al. (2001).