He monitored the enemy's movements using a periscope.

I used an optical microscope for an experiment at school.

When I look into her eyes, it's like I can see her heart. That's because the eyes are the window to the soul.

He wrote a message using mirror writing.

We should always remember the power of Kannon in difficult times.

This ancient proverb, 'know the other side and yourself, and you will not be in danger in a hundred battles', teaches us the importance of understanding ourselves and others.