Experiment based on instructions from Brian Cox in the BBC tv programme Wonders of Life. 1. Everything you will need and more. 2. Swish some saliva around your mouth. Particularly against your cheek to dislodge some cells. Spit into a test tube or similar container. Like Prof Cox, we found this bit more tricky than you'd think. Add some washing up liquid to break down the cells containing the DNA. A little salt aids the process. NB, use less than is shown here - we found that you only need a little bit. Now give it a little shake. Add some vodka. This should float on top of the mixture. Now take a look at what you've got, but be careful that the wind doesn't change. The strands that have risen into the vodka are DNA strands!