Two liquids with approximately the same density can mix together. But two liquids with significantly different density won't mix, like water and oil. They will remain separated one above the other. Stevespanglerscience managed to put 9 different liquids with different density and colors, and so he made a density tower on a transparent glass tube. Then, he dipped inside different objects, such as a bolt, a ping pong ball, a soda cap and others. Amazingly, the objects floated in different layers! Watch the experiment.