Do you know the chickens that lay your eggs? Do you know in what condition they live? Do you know what they eat? Do you know the farmer who grows your vegetables? Do you know about his methods? Do you know about his soil? Do you get your vegetables as soon as they are harvested? Do you know where your meat comes from (if you eat meat)? Have you chatted with the farmer who runs the farm? Do you know his practices? Have you seen how the animals live? Are treated? Find their end?
In former times we knew how all of this worked. Then we lost touch because we went shopping at the supermarket. But when the kids start to believe that eggs, or meat, or apples come from the supermarket it's time to go visit a farm and talk to the farmer.