Two years ago, I discussed how curly arrow pushing is taught, presenting four different ways of showing the arrows. One of the comments posted to that blog suggested that all of the schemes shown below were deficient in one aspect. Curly arrow pushing The issues were the stereo and regiochemistry. In particular, the diagram above carries no explicit information about the symmetry of the electrons from which the first arrow originates;

In 1953, the model of the DNA molecule led to what has become regarded as the most famous scientific diagram of the 20th century.