A sightseeing tour in the world of clusters--serendipity and scientific progress.

The discovery of the fullerenes in 1985 by Kroto et al. and the development of a method for producing macroscopic amounts in 1990 by Krätschmer et al. opened a new area of carbon research and the possibility of producing new materials with unique properties. The field has developed further with discoveries of nanotubes, metal-filled nanotubes, carbon onions, met cars, and metal-covered fullerenes, all of which have unique properties and possible technical applications. In retrospect, it is in interesting that indications of many unique species have existed before their discovery but have not been recognized. In general, it seems that one is so focused on a given problem that one does not realize how many great discoveries or serendipities are "hidden" in available experimental and theoretical data. In addition to generating a lot of scientific progress, these new discoveries in the field of cluster science, and in particular in carbon species such as fullerenes and nanotubes, have opened up the doors to different areas of science such as mesoscopic physics and modern material science. The general trend is from small to large systems, contrary to the general trend of modern mesoscopic physics or microelectronics where the movement is from large to small. It is especially fascinating how the whole area of fullerene research was initiated to solve problems in astrophysics. Originally, Krätschmer and Huffman intended to explain an observed strong extinction from interstellar dust; in experiments they produced a special carbon soot with a characteristic optical absorption known as "camel hump smoke." Furthermore, the original interest of Kroto was also to solve problems in astrophysics, while Osawa in his original paper on calculations of carbon molecules in organic chemistry focused on how different bonding of carbon atoms would give special species. He then found the truncated icosahedral built up of sixty carbons, without noticing its unique structure, which is today the famous C60.