Your baby's the size of a plum!
The average fetus at 12 weeks is about 2.1 inches long and .49 ounces. Now that he/she has gotten pretty much all her parts, her main job is to keep on growing. He/She is about to enter the growth and maturation stage, in which her organs and tissues will grow and develop rapidly. He/She is now developing her reflexes -- if you poke her body, she'll likely move.
It is also opening and closing her fingers and curling her toes, too.