• Our apologies to Jeff Greason for inserting the sentence “Stephen Hawking calls for moon and Mars colonies” into our interview with him. (24 October, p 27). This was the result of an editing glitch. Greason made no such statement to our interviewer.
• The DOI reference in our article reporting the use of paper as a skeleton for growing animal tissue (24 October, p 10) should have read: 10.1073/pnas.0910666106.
• The Copenhagen summit runs for four days longer than our “Instant expert” article suggested: it closes on 18 December (7 November, p 13).
