Book excerpt: This is a text book of 'Applied Micropalaeontology' with number of aspects of the microfossils to make their taxonomy interpretative. Since they were 'once-living microorganisms', it also forms a part of the biological subjects. Besides, it also covers important developments that took place within the last seven decades in the study of foraminifera, ostracoda, calcareous nannoplanktons, diatoms and conodonts by transforming their ecological-data in the 'rich-text' enabling students to understand the trend of their applications in the recent exploration-techniques for oil and other minerals.