Keywords: ISM: clouds – ISM: molecules – ISM: structure – ISM: evolution

1. INTRODUCTION

2.2. An unbiased catalog of molecular clouds

3. MORPHOLOGICAL CLASSIFICATION

3.1. Classificatory criteria

4. THE CHARACTERISTICS OF FILAMENTS AND NON-FILAMENTS

5. DISCUSSION

5.1. Human biases

5.2. Observational effect

6. CONCLUSIONS