Functional part of DNA is called euchromatin, while non-functional part is called heterochromatin.

Answer

**Step-by-Step Solution:**

1. **Understanding Chromatin Structure:**
- Chromatin is the complex of DNA and proteins found in the nucleus of eukaryotic cells. It exists in two forms: euchromatin and heterochromatin.

2. **Defining Euchromatin:**
- Euchromatin is the functional part of DNA. It is less condensed, allowing for easier access to the genetic information. This makes it actively involved in transcription, the process where DNA is copied into RNA.

3. **Characteristics of Euchromatin:**
- Euchromatin appears darkly stained under a microscope due to its loose structure, which allows for better staining. It is primarily located towards the periphery of the nucleus.

4. **Defining Heterochromatin:**
- Heterochromatin, on the other hand, is the non-functional part of DNA. It is more condensed and tightly packed, which makes it inactive in terms of transcription.

5. **Characteristics of Heterochromatin:**
- Heterochromatin appears lightly stained under a microscope because of its dense structure. It is mostly found towards the center of the nucleus and does not participate in the transcription process.

6. **Conclusion:**
- In summary, euchromatin is the functional part of DNA that is actively involved in transcription, while heterochromatin is the non-functional part that is inactive in transcription.