If you've followed environmental stories over the years, you'll know this tune. Scientists have long been singing off the same songbook when it comes to fossil fuels, deforestation and pollution. But drum not often banged is the dwindling supply of phosphorus. It's is an essential element for all life. It makes up our DNA and all organisms need it for energy. It cannot be replaced, there is no synthetic substitute. In other words, without phosphorus, there is no life. This week on the Naked Scientists, we investigate whether we're running out of phosphorus for fertiliser and what we can do about it by getting ourselves knee deep in human sewage... Plus in the news, we'll learning how to hide a secret message with a fizzy drink, we'll be getting up close and personal with the cuddle chemical oxytocin and why Monday's Mercury transit was so exciting!