This research provides a comprehensive classification system for an important group of fungi called Penicillium section Citrina. These fungi are commonly found in soils worldwide and some can produce beneficial or harmful compounds. The researchers used multiple methods including microscopy, growth experiments, chemical analysis, and DNA sequencing to clearly define 39 different species, including 17 newly discovered ones. This improved classification system helps scientists better understand fungal biodiversity and accurately identify these organisms. Impacts on everyday life: – Improved ability to identify potentially harmful or beneficial fungi in soil and indoor environments – Better understanding of fungal diversity helps in agriculture and soil health assessment – More accurate identification of fungi that produce compounds useful in medicine and industry – Enhanced knowledge of fungi that can affect food storage and preservation – Contributes to our understanding of global biodiversity and ecosystem functioning