Knowing the 'what' and the 'why'

Tuantuan and Lele nodded excitedly, rubbing the down jackets!

"Mommy, there are feathers inside here~" Lele said with a grin.

Yan Bingxue smiled and asked, "Then do you know why feathers can be used to make down jackets?"

"Because down jackets are warm to wear!" Lele said with a chuckle.

"Then why are down jackets warm to wear?" Yan Bingxue asked with a smile.

The two little ones were stumped by the question, so Tuantuan and Lele turned to Su Chen for help.

"Daddy, why is that? This question is so hard~" Tuantuan said expectantly as she looked at Su Chen.

"Hahaha, it is a little difficult, but once you know the answer, it won't be hard anymore~" Su Chen said with a smile. The two little ones looked at him seriously.

Su Chen continued, "The reason down jackets keep you warm is that they contain something special: Animal protein fiber. It is precisely because of this fiber that down jackets have heat-retaining properties."

"Animal protein fiber?" Tuantuan and Lele murmured.

Su Chen nodded and said, "That's right, protein fiber. This animal protein fiber contains countless tiny triangular air pockets. It can contract and expand as the temperature changes, regulating temperature by absorbing the heat emitted by the human body and blocking cold air from outside."

Tuantuan and Lele nodded earnestly.

The two little ones picked up a piece of duck down and examined it carefully.

"Little ones, what are you looking at?" Aunt Qin asked with a smile.

"Daddy said there are air pockets in this feather, so I'm looking for them!" Lele answered solemnly.

Lin Xiu smiled and said, "Little one, you can't see those air pockets!"

Su Chen also smiled. "You can't see them with the naked eye. You need a special instrument to see them!"

Lele