I've been wanting regrow my green onions/scallions for a while now.  The first time I tried to do this, my Grandparents were over and my Grandmother thought she would be helpful and clean up the kitchen.  She ended up throwing away my poor stem that I had been taking care of for a few days.  (sigh)

Now I'm off to try this again.  I started by saving the bottom stalks of the scallions (the white portions) then putting them in a glass, root down with a few tablespoons of water.  Within 2 days I could see new growth in the green stems. (yay!) By day 5 it looked like they were growing strong.  Now by day 6, I could literally see the changes overnight.