Green slime became a hit with kids thanks to Nickelodeon's "You Can't Do That on Television" series that aired in the 1980s. You can re-create the gooey slime for your kids, but it might be wise to instruct them to play with it outside.
Mix 1 cup of water and 1 cup of cornstarch together in a medium stainless steel bowl until it becomes gooey and like dough. If it's too watery, add more cornstarch. If it's too thick, add a bit of water to the mixture.
Add food coloring to the mixture. Most slime is green, but you can be creative and add any food coloring.
Mix all ingredients well until you get the desired consistency.