The phrases below have something in common that has nothing to do with their meanings. The common characteristic can be expressed as a familiar expression. Can you determine what it is?

1. Low fat omelet
2. Great omen
3. Roma tomatoes
4. Potato masher
5. Angora tomcat

HINT:
It's a science-based expression.

Answer:

In each phrase the word ATOM is divided between two words, suggesting the expression SPLITTING THE ATOM:

1. low fAT OMelet
2. greAT OMen
3. romA TOMatoes
4. potATO Masher
5. angorA TOMcat

Credit:
Billie Truitt
SPLITTING THE ..............