Place the 4 glasses in a row. Leave the first glass empty. Glass 2: add 1 teaspoon of salt. Glass 3: add 2 teaspoons of salt. Glass 4 (the tallest glass): add 4 teaspoons of salt. 

To each glass, add 3 drops of food colouring (add a different colour to each glass). 

• Hint: try not to have similar colours next to each other​. You could leave glass 2 or 3 colourless. Your tower might look cool with a clear layer.

Pour 60 ml (1/4 cup of hot water) to each glass. Stir each solution until all the sugar is dissolved.

Now you are going create layers in the fourth glass by transferring the solutions from the other glasses using the straw as a pipette. Place the straw all the way to the bottom of the third glass. Hold your finger over the top to keep the liquid in the straw. Move the straw over to the fourth glass.

Turn the spoon upside down and put it inside the fourth glass and touching the side of the glass just above the layer of the coloured solution.

 Release the solution in the straw so that it runs off the back of the spoon onto the top of the first solution.

Keep transferring the solution in this way being careful not to disturb the interface between the two layers.

Repeat this process with the solution in the second glass. 

Then repeat this process with the solution in the first glass. 

You should have 4 layers of solutions.