why can we see our breath in the cold？so that we can make weird shapes.no.our lungs help us to exchange gases.they are always mois

动画 科普 stem stem动画 动画stem 2025-09-15 05:17  2

Why do people go bald？How would I know？I will explain.Our hair grows from hair follidles.We have about 100，000 hairs on our head.E

动画 科普 stem stem动画 动画stem 2025-09-14 21:15  3

Pollen forming a tiny ice crystal。However，when water freezes，its molecules arrange themselves in a hexagonal pattern.

动画 科普 snowflakes stem动画 动画stem 2025-06-07 00:42  8