I used to grow plants in cups on window sills. You can do it. You don't have to have a grow light. I had garlic growing in the window but moved it to the top of my refrigerator. This is just a lamp with CFL bulbs. The garlic needs more light, but this is just to help me through winter. The container needs to be shallower so the light can be bent closer. I am really just trying this tomatoes are what I really want up there. Just one or two early ones to put in a pot.