Upon entering the Minish Woods, proceed through the winding paths. You'll eventually come across a strange, talking cap being attacked by Octoroks. This is Ezlo. Defeat the Octoroks to rescue him. After a brief, humorous introduction, Ezlo will reluctantly join you, perching himself on your head. He will then grant you the ability to shrink and grow at specific glowing portals.
Ezlo is not just a talking cap; he's your guide, offering hints and advice throughout your journey. His ability to shrink Link is fundamental to solving many puzzles and accessing areas that are otherwise unreachable. The first shrinking portal is located immediately after you meet Ezlo. Step onto it and press the L button to shrink. This will open up new paths and reveal the world from a Minish perspective. Get used to switching between your normal and Minish sizes, as it's a core mechanic.