A seedling is a young sporophyte sprouting developing out an embryo from seed. The development of a seedling begins with germination of seed. Seedlings consist of three main parts: -The Radicle (Embryonic Root) -The Hypocotyl (Embryonic Shoot) -Cotyledons (Seed leaves) in this process soil temperature is important, cool soil retains the germination process, warm soil about 75 if possible until seedings show up in your soils surface. Provide adequate air temperature of 70 to 75 during the day and at night temperatures of at least 60 to 65. water daily until seedlings are at least a few inches tall or wide, hot or windy conditions, check the soil often and water frequently as conditions sometimes dry the soil much faster. Avoid wet leaves it helps prevent diseases. Before transplanting seedling outdoors my rule of thumb is seedlings should have at least 3 to 4 leaves we call that "True Leaves" by then it should be big enough to plant outside after it has been hardened off.