One makes you small
PillAfterbirthUnlocked
How do you unlock One makes you small?
Verified starting unlockSource data confirms that no unlock is required.
Decreases Isaac's size and increases the pitch of his voice. This effect decreases the size of Isaac's hitbox; a small enough hitbox allows Isaac to walk "under" certain projectiles to avoid them.
Available from the start
No unlock needed — this is available in every new save file.
What unlocking One makes you small leads to
Nothing depends on this yet.
Source: bindingofisaacrebirth.wiki.gg
Imported 2026-09-13