Hydroponic farming. Original public domain image from Flickr https://www.rawpixel.com/image/3370630/free-photo-image-greenhouse-farm-plant-agricultureFree Image from public domain licenseThe hydroculturely-grown butterhead lettuce grown in the Sirmon Farms greenhouse, which regulates the oxygen and nutrients… https://www.rawpixel.com/image/3259567/free-photo-image-hydroponic-butterhead-lettuceFree Image from public domain license