Magnetic Resonance Imaging "sees" inside the body by mapping the position of water molecules, which exist at different densities in different types of tissue. A video of MRI images of the human body in action is as fascinating as it is spooky.
You can see a set of twins inside a womb, with the friskier one kicking its arms and legs out and a baby being squeezed out of the vagina during a live birth. The process of two individuals kissing is especially intriguing when you see the heart of one start to beat faster.
The rhythm of sex is hypnotizing but you realize how clinical the intimate act looks when seen through an MRI machine. Watch the magic here.