The apple of (one's) eye old-fashioned
Have a strong feeling of affection for someone or something
Jane is always praised by her teacher.. Probably, she is the apple of her teacher's eye.
Since his ingenious plan spectacularly succeeded in saving the company on the verge of bankruptcy, he has become the apple of his boss's eye.
This wristwatch is the apple of my eye as it not only is my family heirloom but also associates with several indelibly memories of mine.
If you are in/get into somebody's good/bad books, you have/not have their favour.
To give someone or something better treatment than others.
A subject one knows a lot about, or likes a lot
The term initially had an anatomical meaning and was used to refer to the pupil. Gregory's Pastoral Care, a work credited to King Aelfred (the Great) of Wessex, first used the term in Old English in 885 AD. Shakespeare included it in his play A Midsummer Night's Dream in 1600, and it also appeared in English Bible translations in 1611. However, after appearing in Sir Walter Scott's novel Old Mortality in 1816, the term became more widely used.