1. INTRODUCTION  
2. STELLAR PARAMETERS  
2.1. Gaia  
2.2. Ages Derivation  
3. CLUSTERING ALGORITHM  
3.1. Methodology  
3.2. Synthetic Tests  
4. RESULTS  
4.1. Orion C and D  
4.2. Orion A  
4.3. Orion B  
4.4. λ Ori  
5. CONCLUSIONS