How many megapixels is my eye?

This week, what's the resolution of the human eye? Would nanobots be attacked by our immune systems? How small would a squash ball lump of coal be if you squished it into a diamond? Why do propellers look like they change speed, or even go backwards? And why do men's hairlines recede? Plus in the news, what's happening with this new coronavirus in China? Dr Chris chats with Kieno Kammies...