We knew there had to be a delay in this, but we had no idea how it occurred.

We knew that the heart starts to pump at around 9.5 days.

We learn a lot by taking cells out, chopping them up, and looking at individual molecules. But it doesn't tell us what we need to know about the complex interactions between cells.

There's so much background light and reflection and motion that you need something very bright to be able to detect these cellular signals.

These cells have to die, because if they didn't the heart would not function properly.