Complex sentence: The extremely small cell size means they are incapable of being examined by light microscopy; a stereomicroscope is required for viewing the morphology of "M. pneumoniae" colonies, which are usually less than 100 µm in length.
Split into simpler sentences: The extremely small cell size means they are incapable of being examined by light microscopy and therefore a stereomicroscope is required for viewing morphology. In addition, "M. pneumoniae" colonies are usually less than 100 µm in length.