Many of us used to spend hours playing outdoors in our childhood. We were cycling, climbing trees, digging pits in the backyard. We would collect stones, cones, garbage, and do new things from them. Although we did not know their names, we would have examined the flowers, buds, weeds, insects in the garden. From morning till evening, until someone called us home, we played carefree and carefree. In short, most of our daily life would be in the open air.