Hello and welcome.
Today it's cool and rainy in Tokyo.
Our idiom for today is keep an eye on... something.
This means to closely watch something or someone.
Example 1
Would you please keep an eye on my bag while I go to the bathroom?
Example 2
We'll have to keep an eye on our investment. If it drops too much, then we'll have to sell.
Example 3
I'll have to keep an eye on the steaks. I don't want to burn them like I did last time.