Pokémon FireRed and LeafGreen/Route 2

When you're done in ../Route 22/, make your way back to Viridian City and exit through the north path to reach Route 2. Much of this route is inaccessible to you this early on, but you'll be able to reach it later after acquiring HM 01. For now, your only concern is reaching the entrance to Viridian Forest. Pick up a Pidgey or Rattata if you haven't caught one yet, but don't bother hunting for Caterpies or Weedles, they're more plentiful in the forest.



Second visit
After you beat LT. Surge in Vermilion's Gym, you will be able to return to Route 2 through Diglett's Cave. You will get to the area which you couldn't get to in the beginning of the game. There's a trade as well as some items that you couldn't reach before.

Trades
Don't bother trying to find where this trade can take place just yet. You'll have to wait until you reach a place known as Digglet's Cave. Travel the cave and you'll be back in this route, where the trainer holding Mr. Mime will await you.

Items

 * HM 05 (P. Oak's assistant)
 * Ether
 * Paralyze Heal