Description: Why does the floor get so hot? When winter break begins, Gyeoul and Yeoul go to stay at their grandfather's house in the countryside. After a fun day sledding in the rice fields, they come home to find their grandfather lighting a fire in the agungi (traditional wood-burning stove). The flames warm their frozen bodies and roast delicious sweet potatoes in the ashes. Gyeoul and Yeoul try feeding firewood into the fire themselves, learning how firewood is gathered and how the fire in the agungi warms the whole room. The wood they add crackles and burns brightly. After a warm dinner, the two children fall into a deep sleep. But why does the room keep getting hotter and hotter as the night goes on? Ondol: The Efficient, Scientific Heating Method the World Is Watching Gyeoul and Yeoul's grandfather's house is a hanok, a traditional Korean house, and the room is an ondol room, heated by a fire in the agungi. It gets so warm that people say it feels like your body is being "steamed." Why does an ondol room get so toasty? Ondol is a heating system that warms flat stones called gudeuljang beneath the floor, and the heated floor in turn warms the air in the room. This method heats the floor evenly, retains warmth in the stones for a long time, prevents excess moisture, and is relatively safe with little risk of fire. Unlike Western heating methods that warm the air directly, hanok heat both the floor and the air together, making it a more efficient and economical heating method that is drawing international attention. Used since the Three Kingdoms period, ondol is a heating method unique to Korea, found only in Korea and the northeastern region of China. Thanks to ondol, Korean culture developed a floor-sitting lifestyle. Today, we no longer use traditional ondol very often. As lifestyles have become more Westernized, house structures have changed, and people now live more conveniently with furniture like chairs and beds. As a result, the wood-fired ondol can now mostly be seen only occasionally in old countryside homes. However, the principle of heating through the floor lives on today in modern boiler systems. Now more than ever, we need to make an effort to preserve our unique traditional culture while also developing it in modern ways. Traditional Culture Education: From Kindergarten Nuri Curriculum to Elementary School Textbooks Traditional culture is an important topic within the "Social Relationships" area of the Nuri Curriculum, covering Korea's traditions and culture. This emphasis continues into the revised elementary school textbooks for grades 1–2, where the focus on traditional culture education has grown even further. This reflects the increasing importance placed on fostering a sense of community. Among the many things children learn during their kindergarten years, understanding traditional culture has become increasingly significant. Let children discover and enjoy these lessons naturally through picture books. ■ About the Yellow Umbrella Traditional Culture Picture Book Series 1. Our Child Is Missing! – Stories of the household guardian spirits who protect every corner of the home 2. Make Way! Here Comes the King of Ttakji – Stories of traditional Korean games like biseokchigi, gonggi, hoop rolling, and jump rope 3. I Love Hanbok, Our Beautiful Traditional Clothes – The story of hanbok, which is becoming more popular and beloved around the world 4. I Want to Bow on Chuseok Too – Stories about Korean holidays, from eating songpyeon to dancing ganggangsullae 5. Millstone, How Absurd! – Stories of traditional Korean household tools like the tteoksiru, mortar, cauldron, and winnowing basket 6. Shh! The Secret of the Jar – The story of the breathable, scientific, eco-friendly, and forward-thinking traditional Korean jar 7. The Sizzling Floor, the Toasty Bottom – The story of ondol, the efficient heating system that warms both floor and air together