"Would you like a piece of chocolate, darling?" Millie looks up at her grandmother in delight. "Yes, please!" she says, and holds out her hand for the delicious-looking dark square. But when she pops it in her mouth - "Ugh!" It is the most disgusting thing she has ever tasted: not the milk chocolate she was expecting, but dark chocolate. How horrible!

Few things divide people as fundamentally as chocolate. Some people like dark, some people like milk - but hardly anyone likes both. When The Washington Post ran an article about which was better, it received 5,000 letters on the subject.

Chocolate is made from the seeds of the cacao tree - also, confusingly, known as cocoa beans - and was originally drunk rather than eaten. Archaeologists have found evidence of it in Mexico dating from 1900 BC.

Chocolate was unknown in Europe until Christopher ColumbusA 15th Century Italian explorer and navigator whose trips across the Atlantic opened the way for European colonisation of the Americas. brought back cocoa beans from America in the 16^th Century. It gradually became fashionable, and people began buying it in a solid form. Paris established itself as a leading chocolate-making centre: one of the leaders of the French RevolutionThe overthrow (and subsequent execution) of France's king and aristocratic government in 1789. The revolution became infamous and influential worldwide., Pauline Leon, came from a family of chocolatiers.

From the early 19th Century chocolate bars were produced on an industrial scale. Then, in the 1850s, a Swiss businessman called Daniel Peter invented milk chocolate by adding milk powder to them. This was a breakthrough because cocoa beans in their natural state are extremely bitter, so many people did not like chocolate at all.

According to Megan Garber, writing in The Atlantic, "Dark chocolate has a more pronounced chocolate taste than milk chocolate, because it does not contain milk solids to compete with the chocolate taste. However, the lack of milk additives also means that dark chocolate is more prone to a dry, chalky texture and a bitter aftertaste."

Many bars today come with wrapping which boasts how much cacao they contain. Dark chocolate is defined as anything which is at least 35% cacao.

Some people believe that the higher the percentage, the better the chocolate. But according to one expert, Darren Williams, "Once you get past the high 70s and low 80s, you're onto a very bitter, almost astringentAn acidic or bitter taste or smell. chocolate which starts to lose the flavour of the bean. 100% is only good for cooking."

Scientists say that dark chocolate can be good for you, because it contains antioxidantsSubstances that prevent or delay some types of cell damage. called flavanols which help reduce blood pressure. And according to Professor Jeffrey Blumberg of Tufts University,¹ "Some research suggests that milk may interfere with the absorption of flavanols."

But which you prefer may depend on your parents. Research in the US suggests that some people have a gene which make them more receptive to caffeine than others, and more addicted to the boost in mental alertness that it gives them. And, says Professor Marilyn Cornelis,² "When they think of caffeine, they think of a bitter taste, so they also enjoy dark chocolate."

Yes: It tastes much sweeter. Dark chocolate was drunk by the AztecsThe most powerful Central American civilisation in 1492, when Europeans first made sustained contact with the Americans. Their civilisation was destroyed by the Spanish, who enslaved what was left of their people., who were keen on human sacrifice and sometimes mixed it with blood, so it has a dark history as well as appearance.

No: Milk chocolate does not have the same health benefits as dark, because the milk interferes with the flavanols which help your blood pressure. The more bitter chocolate is, the better.

Or... No chocolate is really good for you. It is bad for your teeth and in too great a quantity, bad for your health. It also melts easily and ends up as a sticky mess.