pick up on

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb transitive, idiomatic To notice, observe, learn, or understand, especially something otherwise overlooked.
• verb transitive, idiomatic To continue or build upon (for example, a task, analysis, or narrative), beginning from a point at which someone has previously stopped.
• verb transitive, idiomatic To adopt a practice in which others already engage.