How do i warm my plants!

how can i warm 2 of my seedlings kuzz im growing in window sill gets really really cold at night culd i use a coffee warmer with a coffe cup holding the actual plant cup like inside eachother and cofee cup has water in it wuld the steam hurt my plant?

heating pad under the pots would work well hope this helps

Happy Growing!

I left my plant outside in pretty cold temps, probably 40s and 50s and it is fine.