The Minitta Machine is the name of a machine found in the Water Temple that allows Tomba to shrink in size so he can enter tiny doors and passages.
In order to use the machine, the Tiny Tomba/Mini Tomba event must be cleared, where the cogs from the Wind it Up!, Raise the Ladder!, Use the Seesaw! and Open the Water Gate events must be gathered. The Minitta Bell, which Tomba receives directly after the Tiny Tomba/Mini Tomba event, can be used to teleport Tomba to the machine anytime.
The Minitta Mushroom, which can be obtained by clearing the Tiny Mouse's Berry Nuts event, has the same effects as the machine, allowing Tomba to shrink or grow without using the Minitta Machine.