Covid-19 group  Inclusion Criteria:  (Past) Positive SARS-CoV-2 Infection (PCR proven) Age 5 to <18 years  Exclusion Criteria:  Acute SARS-CoV-2 Infection and Isolation Quarantine Pregnancy Critical Illness No consent to LF_MRI General contraindications for LF-MRI, such as electrical implants, pace makers, perfusion pumps)  Healthy controls  Inclusion Criteria:  - Age 5 to <18 years  Exclusion Criteria:  (Past) Positive SARS-CoV-2 Infection (PCR or antigen test proven) Suspect for lung disease Acute respiratory infection/symptomatic Acute SARS-CoV-2 Infection and Isolation Quarantine Pregnancy Critical Illness No consent to LF_MRI General contraindications for LF-MRI, such as electrical implants, pace makers, perfusion pumps)