1: Sheldon and Amy's Nobel Prize win.

2: Howard and Bernadette's parenting struggles.

3: Raj's search for love and happiness.

4: Penny's success in her acting career.

5: Leonard and Penny's romantic milestones.

6: The origins of the Big Bang Theory gang.

7: The hilarious antics of the group's friendship.

8: Crossover episodes with other popular TV shows.

9: Exciting new adventures in the Big Bang Theory universe.