It is the smallest unit of life that is classified as a living thing, and is often called the building block of life.
"I saw that baby trying to get away from the probe that the doctor was using…I just wanted to make it stop…I could see it twisting..."
"For many years, this was done via blatant lies. It's not really a baby. It's just a blob of cells. Just tissue. No different than blood. That has changed."