1. INTRODUCTION
2.1. ALMA and VLA Observations
2.2. The Orion Sample
2.3. The Perseus Sample
2.4. Data Analysis
3. OBSERVATIONS OF MULTIPLE PROTOSTARS IN ORION
3.1. Overview of Multiplicity Detections
3.2. Multiple Systems with < 500 au Separation
3.3. Close Multiples Not Detected By Both ALMA and VLA
3.4. Impact of Non-detections or Spurious Detections
3.5. Dynamic Range of Detected Systems
3.6. Near-infrared vs. ALMA/VLA Detections
4. OVERALL MULTIPLICITY CHARACTERIZATION
4.1. Bolometric Luminosities and Temperatures
4.2. Separation Distributions
4.3. Quantitative Separation Distribution Comparisons
4.4. Overall Multiplicity Statistics
4.5. Relationship Between Multiplicity and YSO Density
5. DISCUSSION
5.1. Formation Mechanisms of Multiple Systems
5.2. Future Evolution of the Companions
5.3. Multiplicity Variation with YSO Density: A Sign of Migration?
5.4. Multiplicity of Class I and Flat Spectrum Protostars and Impact on Class Lifetime
5.5. Coevality of Multiples
6. CONCLUSIONS