The subject (EHS) has its own significance to provide the sound and deep knowledge regarding the Sikkim state in a holistic approach for the students and SPSC learners. It deals with many aspects of the state from comprehensive details about the Eastern Himalayan range, Brief ancient History, Geographical Regionalization, Land formation, Soils, Drainage systems, Geo-setting, Relief, Soil-Biodiversity and Bio-resources, mighty Rivers of Sikkim, Planning commission of India (agro-climate regionalization), Minerals resources, Climate-Drainage system, Communities and their Culture, Traditional Healing Practices, Economy- Agriculture, Industry (Tea & Tourism). Critical Environmental Issues Development Bottlenecks: With special reference to Hydro-resources, Communication and Pharmaceutical Industrial, Climate Change, Natural Hazards and Disaster Management and Degradation of Bio-Resources.