Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Once the meditator achieves a strong and powerful concentration (jhana, Sanskrit dhyana), his mind is ready to penetrate and gain insight (vipassana) into the ultimate nature of reality, eventually obtaining release from all suffering. The cultivation of mindfulness is essential to mental concentration, which is needed to achieve insight.
What is powerful concentration called?