Your baby weighs about 5 ounces now, and he's around 5 inches long — about the size of a large onion. He can move his joints, and his skeleton — until now rubbery cartilage — is starting to harden to bone. His sense of hearing is also developing. The umbilical cord, his lifeline to the placenta, is growing stronger and thicker.
I don't really like the comparison to an onion, but I guess that it helps with understanding the size. But still... an onion?