1) Meteorite 2) Micrometeor 3) Micrometeorite 1) Micro meteor 2) Micrometeorite 
A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeorite is such a particle that survives passage through the Earth`s atmosphere and reaches the Earth`s surface. ==Scientific interest== Micrometeoroids are very small pieces of rock or metal broken off from larger chunks of rock .....
Meteoroid less than 1/250th of an inch in diameter.