There are 200 different kinds of cells in the human body, from brain cells, to blood cells, to nerve cells, to intestinal cells, and beyond. One of the most fascinating is the heart cell, which — when enough of them grow together to form into heart muscle fiber — begin to involuntarily twitch in unison. Now scientists have recently added an extra layer of awesomeness by growing twitching muscle cells in a lab for the very first time! The muscle fiber they grew is able to twitch in response to drugs, electrical pulses and biochemical signals. You can watch the video above, and read more about how lab-grown muscles open the door to exciting treatment options for patients, by visiting VOX.com.