which is better, cryptography in network security or cryptography in...

...biology (DNA crypto etc.) ? Hi....i'm a student of bachelors in computer science, and im in 4th semester...i want to be a cryptologist, but i don't understand which is better...i have searched alot on cryptography in network security......nd i have also found that there is a DNA cryptography...so i'm confused that which is better...and whose scope is best in the future......
kindly guide me through this......thanx in advance.....