I have been working on ferns since 1980, starting at the Rijksherbarium Leiden, which is now morphed into the Botany section of the Naturalis Biodivesity Center. I have tackled a number of families and genera, always with the goal to find out how many (some would say, how few) species there really are. The main focus of my work has been on the Malesian part of the world (basically, Indonesia and surrounding countries), but I have also worked on the flora of China and Sri Lanka.