Heterochromatin is a very tight and condensed form of chromatin.
Heterochromatin is very stable.
Heterochromatin is present in a very condensed form inside the nucleus that’s why it appears as small, darkly staining irregular particles inside the nucleus.
Euchromatin:
Euchromatin is a loosely packed form of chromatin.
That’s why DNA is more accessible.
This type of chromatin is involved in the active transcription of DNA into mRNA.