In the 1 cup of water, add 8-10 drops of food coloring and mix

Place corn starch into a bowl and add the green water

Mix together with a spoon, it’ll be hard but keep mixing. If it seems a little dry, then add a little bit more water.

It’s like a solid and liquid at the same time and it's called A non-Newtonian fluid. Form it into a ball and watch it melt into a liquid through your fingers