1. INTRODUCTION

2. ADOPTED PANCHROMATIC DATA OF NGC 6781
2.1. Photometry data
2.2. Spectroscopy data

3. THE MULTI-COMPONENT NATURE OF NGC 6781
3.1. The ionized gas component
3.2. The molecular gas component
3.3. The dust component: summary of HerPlaNS I
3.4. The central star

4. CLOUDY DUSTY PHOTOIONIZATION MODELS
4.1. Modeling approach
4.2. The input model
4.3. Results and discussion

5. CONCLUSIONS