If you intend starting seedlings off indoors on a window sill, here's a neat trick to stop them going leggy and bending towards the light.
Take a cardboard box just big enough to accomodate the seed tray/pots, cut one side off it and line the remaining 3 sides with aluminium foil.
Place the box on the window sill with the cut out side facing the window. The light will be reflected back at the seedlings, nearly doubling the amount of available light and providing all round, rather than omni-directional illumination.
If you can't be bothered to faff about with a box, take a decent length of foil, place some underneath the seed tray and then simply fold it upwards. A quick nip & tuck here & there and it's self supporting. (That's how I do it).