Dr Richard Clay goes in search of what it is that has made us scribble and scratch mementoes of our lives for more than 30,000 years. From the prehistoric cave paintings of Burgundy in France, through gladiatorial fan worship in Roman Lyons to the messages left on the walls of Germany's Reichstag in 1945 by triumphant Soviet troops, time and again we have wanted to leave a permanent record of our existence for our descendants. And it may be that this is where what today we call art comes from - the humble scratch, graffiti.

Interviews with those close to the talented footballer reveal the different factors which may have contributed to his untimely end.

在城市街道的下面，潜伏着某种邪恶的东西——油脂块。这些凝结的脂肪和人类排泄物是我们冲进马桶和水槽的产物。我们为什么会突然关注它们？在这部令人震惊的纪录片中，一组专家剖检了一个重达5吨的样本，样本取自一个至少750米长的油脂块。它的成分是什么？它将揭示怎样的人类秘密？有趣的发现揭示了油脂块可能存在的致命威胁，以及我们可以对我们的习惯做出的简单改变，从而使我们的下水道更安全。