The use of natural catalysts - enzymes - for the transformation of non-natural is not at all new: they have been used for more man-made organic compounds than one hundred years, employed either as whole cells, cell organelles or isolated enzymes [1]. Certainly, the object of most of the early research was totally different from that of the present day. Thus the elucidation of biochemical pathways and enzyme mechanisms was in the foreground of the reasearch some decades ago. It was mainly during the 1980s that the enormous potential of applying natural catalysts to transform non-natural organic compounds was recognized. What started as a trend in the late 1970s could almost be called a fashion in synthetic organic chemistry in the 1990s. Although the early euphoria during the ''gold rush'' in this field seems to have eased somewhat, there is still no limit to be seen for the future development of such methods. As a result of this extensive, recent research, there have been an estimated 5000 papers published on the subject [2]. To collate these data as a kind of ''super-review'' would clearly be an impossible task and, furthermore, such a hypothetical book would be unpalatable for the non-expert.
