Final answer:
Heterochromatin is the most highly condensed form of chromatin, representing regions with inactive genes, contrasted with the less condensed euchromatin containing active genes.
Step-by-step explanation:
The most highly condensed form of chromatin is heterochromatin. Chromatin can be found in different states of compaction based on the cell cycle and gene activity. Euchromatin is the less condensed form and contains genes that are actively being transcribed, whereas heterochromatin is much more condensed and is generally gene-poor or contains inactive genes. During interphase, euchromatin and heterochromatin can be distinguished, with heterochromatin being tightly packed. However, it is during mitosis that chromatin reaches the highest level of compaction into chromosomes, facilitated by multiple layers of organization: DNA wrapped into nucleosomes, which further coil into a 30-nm fiber, and finally, the fibers are packed together with scaffolding proteins to form the metaphase chromosomes.