young blood

noun3

1. •
   Young or youthful people, especially as a source of revitalizing force (in a team, organization, etc.).

   • Young blood must have its course, lad, and every dog its day. — 1862
2. •
   A young person (especially a man); also as a term of address.
3. •
   Youthful, revitalizing, or youth-oriented ideas.