My perceptions of the biohydrometallurgical field span four decades and stem from being a professional microbiologist conducting academic research and research for process development and applications. My experiences have given me an appreciation for knowledge gained through fundamental research and the transfer of this knowledge to development of commercial scale applications of microbial processes. The symposia series for international activities in biohydrometallurgy has been a major factor in advancing knowledge and applications for microbial bioleach systems. The first international biohydrometallurgy meeting was held in Braunschweig, Germany in 1977. This was the predecessor for the International Biohydrometallurgy Symposia. As evident from the Symposia, advances in development and applications of biohydrometallurgy technologies follow an evolutionary, rather than revolutionary progression from demonstration of knowledge at the laboratory scale to engineering commercial plants.