Scale bar represents 10µm
Nuclear speckles are a non-membrane bound nuclear sub-compartment that contain pre mRNA splicing factors. Besides the storage of those splicing factors nuclear speckles are thought to serve as a regulatory site for transcription among other things.
Nuclear speckles show an irregular, mottled staining pattern inside the nucleoplasm that varies in size and shape between different cell lines.
Read more about the nuclear proteome.