How do you make one of those desk decorations filled with colored liquid and you turn upside down and droplets

Question

go up and down?

my son wants to make his own present for someone.
we have a tall jar, some food coloring and some oil.
do we need glycerol or some kind of thickener?

Answer 1

http://www.psychicgoldfish.com/sub_page/whatido/lavalamp.htm
http://www.exploratorium.edu/science_explorer/volcano.html
http://www.wikihow.com/Make-a-Lava-Lamp-with-Household-Ingredients