Transcript for Instant Index: Conjoined Twins Christmas Miracle
And now, our "instant index." And it starts with a very special christmas portrait. Allison and amelia tucker with santa. 10 months old. So, what makes it amazing? Well, these girls were born joined at the chest. Sharing a diaphragm and a liver until 40 doctors separated them in a christmas miracle. So, when santa came to the hospital in philadelphia, each baby had a separate perch on santa's knees. The smalleof the two w home today. The other will stay through the holidays, but both are expected to live full and healthy lives. And, we have two postcards from the extreme cold. First, this is a snapshot from the north pole and look. It's like a field of flowers on the ice. But yourceiving you. They are called frost flowers. Icy bouquets that rise up when cold water collides with even colder air. And, a video from icy siberia, where they want us to know what it's like to wake up to 40 degree below zero. This man took a pot of boiling water off the stove, tossed it outside to show you. Within seconds, it becomes icy sleet. That was boiling water. A little perspective on our winter goose bumps. And we do want to hear from you. Tweet me your thoughts for "instant index" @diane sawyer.
This transcript has been automatically generated and may not be 100% accurate.