Science, Technology and Innovation for A Clean, Green and Healthy Nation Clean, green and healthy are some common words of discussions in the context of planning and development since days of the evolution of the concept of welfare economics. It was started with measuring utility in terms of monetary value of social welfare, where life expectancy, per capita income, literacy, employment rate, etc. are considered as indicators, instead of only Gross Domestic Product (GDP) to measure growth . The progression of idea led to the concept of Human Development Index (HDI), with broad consideration of long and healthy life, knowledge and standard of living, taking into account Gender Development Index (GDI) considering variation of situation in the context of man and woman. However, all these approaches are more or less anthropocentric in nature where status of ecosystems was not in prime consideration in assessing human progression. Brundtland Commission’s Report on sustainability brings new light to the concept of sustainable development by interlinking ecology, economy and society and providing the core functionality of Sustainable development . Here, ecosystem or ecological sustainability deals with eco-system integrity, carrying capacity, protecting and managing biodiversity. Economic sustainability focuses on growth, development, productivity and benefits at grassroots; whereas, social sustainability focuses on equity, empowerment, accessibility, participation, sharing, cultural identity and institutional stability. In the contemporary period after reviewing through the challenges of development, Millennium Development Goals (MDG) were conceptualized in 2000. The MDG focussed on eradicating poverty and hunger, attaining universal primary education, gender equality and empowerment, reduce child mortality, improve maternal health, and ensure environmental sustainability through its respective goals. Later on, after reviewing the progress of MDG in July 2014, the UN General Assembly’s Open Working Group (OWG) proposed a new set of agenda with 17 goals to be put forward for the General Assembly’s approval in September 2015. That document set the ground for Sustainable Development Goals (SDGs) and the global development agenda spanning from 2015-2030. In SDG, cleanliness, environmentally sound sanitation and health focused with emphasis including No poverty, Zero hunger, Good health and Wellbeing, Clean water and Sanitation, Responsible consumption and production, Climate action, Life below water, Life on land through its goals -1,2,6, 12,13, 14 and 15 along with other focuses. It is noteworthy that in the spirit of SDG, India also launched its own mission of Clean India ( Swachh Bharat Abhiyan) in 2014. In this perspective leveraging through application of science, appropriate technological facilitation and capacity building are the means for implementation of goals of SDG and other national missions. Therefore the focal theme for National Children’s Science Congress – 2018 and 2019 has been decided as “Science, Technology and Innovation (STI) for a Clean, Green and Healthy Nation”. The focal theme has been designed considering the following operational definition and desired dimension In fact, natural resources in general, and water in particular, along with sanitation and health are integral parts of ecosystem, economy and society. Sustainability of an ecosystem, economy and society depends on sustainable natural resource management, water and sanitation related practices and their management; which regulate the status of health and environmental security. Ecological base of a region with its abiotic and biotic attributes determine the state of availability of natural resources and ecological services. Overuse of natural resources and associated practices are responsible for degradation of ecological security. When the amount of exploitation of natural resources exceeds its carrying capacity, it gives rise to ecosystem disturbances with implications on ecosystem’s health. On the other hand, practices of sanitation are a major responsible factor not only for degradation of water quality but also for degradation of environmental services from an ecosystem