Resident Kage Seraph was the first one who made a tiny avatar in Second Life. Tinies can't be created by just lowering the size of an avatar, via the appearance menu, since the smallest avatar size is still too tall for a tiny. They need special animations to fold/crush the avatar to a tiny size. Afterwards, prims and invisiprims are used to hide the rest of the regular avatar mesh.
The option to upload rigged mesh to the Second Life grid also made it possible to create small mesh avatars, often not bigger then 1/4 or a 1/3 of the normal sized avatar. The regular avatar mesh is hidden by wearing an alpha layer and the rigged tiny mesh body is worn as an attachment.