There has been a significant rise in the number of children with rickets. This has resulted from the airless, indoor world we have created for ourselves. Rickets is caused by a deficiency of vitamin D, which is produced in response to sunlight on the skin. Where children used to play outside they mostly stay indoors immersed in virtual realities via various electronic media. Instead of long summer evenings outdoors, we close the curtains to prevent sunlight falling on our screens. The lure of technology is compounded by adult fears of the risks to children if they are left to roam free in the outside world; in any case there are fewer accessible public spaces for open air activity. Curing this will require an awful lot more than vitamin pills.