be in (one's) element

To be doing something that one is very comfortable with or proficient in. My mother is in her element in the kitchen and can make just about any dish.

Common Names:

Name	Pronounced	Usage
Jaqueline	JAK-ə-leen (English), JAK-ə-lin (English)	English (Modern), Portuguese (Brazilian)
Euclid	YOO-klid (English)	Ancient Greek (Anglicized)
Neptunus	-	Roman Mythology
Kerttu	KERT-too	Finnish
Nkiruka	-	Western African, Igbo
Shaquila	-	English (Rare)