This animation shows how stem cells from early mammalian embryos can be grown and studied in a laboratory.

All cells in the body of a human, or other placental mammal, originate from a group of embryonic stem cells called the inner cell mass (ICM). The ICM is formed during an early stage of development called the blastocyst. As shown in the animation, cells from the ICM can be removed from a blastocyst and grown in a lab indefinitely. Various growth factors cause these cells to differentiate into specialized cells, such as muscle or nerve cells.

This animation is a clip from a 2006 Holiday Lecture Series, Potent Biology: Stem Cells, Cloning, and Regeneration. Depending on students’ background, it may be helpful to pause the animation at various points to discuss different steps in the process.