From Nature:
PhD programmes often lead to an increasing narrowness and specialization, which results in graduate students who are not sufficiently exposed to wider aspects of their subject and of related subjects. Looking outside the immediate interests of a thesis project can lead to real creative advances. One way to expand thinking is to ensure that students have access to a series of inspirational speakers who will cover a wide range of scientific topics, with at least some who are more removed from their PhD focus. At the Francis Crick Institute, we will cover a wide range of biomedicine with truly inspirational speakers, but also look at other areas of science, such as high-energy physics, dark matter and aspects of biology, such as evolution and ecology, that are more distant from biomedicine.
Another suggestion is for what I call 'master classes', after the model of players of musical instruments. In science master classes, a group of graduate students would be exposed to a true expert, an excellent practitioner who would talk about doing science. I don't mean discussing the details of experiments, but discussing the broader questions: how do you do a satisfactory experiment, how do you do rigorous work, what is the nature of knowledge and so on. The final suggestion is to broaden expectations. When students are three-quarters of the way through their graduate degree, they should be intensively mentored and urged to discuss their future careers.