Seedlings are up under lights and growing. It is time to transplant them. When the seedlings have at least their first set of true leaves it is time to transplant them. True leaves are the second leaves the seedling get. They will look like the plant when it is grown. Why transplant? It gives the plant a chance to get a good strong root system and it slows down the top growth.
There are a few tools you need for transplanting especially if you started your seed in a larger container and not in peat pots or jiffy pods. I use a baby spoon, a wood skewer and maybe a 1/4-3/8" dowel. You will also need something to transplant into. I use 6 cell market packs for most things because I sell and that will be their permanent home until they are sold. Since I use pro mix for everything again will get that moist and fill the cell packs to the top. Now there are many other recycled items you can use. Styrofoam cup with holes in the bottom. Yogurt cups and I am sure there are many other things. Using the skewer or dowel make a hole in the medium to plant your little seedling. With the small spoon dig deep and loosen and remove as few seedling as possible with one scoop. If you have planted too thick like I sometimes do you need to gently separate the seedling trying to leave as much medium as possible on the roots. This is where the point of the skewer comes in handy to help separate the roots. Always pick the seedling up by the leaves not the stem as the stems will break very easily. Place the seedling in the hole you have made and gently pack the medium around it. Now when I transplant most seedling I bury the stem up to the leaves just so they are not touching the soil. This will help to keep the plant short and develop more roots. When I transplant is the first time I fertilize. I use 3-10-3 fertilizer diluted at half strength. Reason for this particular fertilizer is the middle # is the ratio of phosphorus in the fertilizer which is important to good root growth and that is what you are looking for at this point. Back under the lights no more that 2" away and don't over water. Check them everyday however for moisture. At this stage I always bottom water.