Objective: 1. To assess the effect of HBOT on Treg, mesanchymal stem cells, and pro-inflammatory cytokines ratio in pediatric population with new-onset T1DM Secondary 2. To assess the effect of HBOT on beta cell reserve in pediatric population with new-onset T1DM 3. To assess the effect of HBOT on glycemic control parameters including time in range, HbA1c and daily insulin dose, in the pediatric population with new-onset T1DM Study design: Randomized, controlled study of pediatric and young adults patients who have been newly diagnosed with type 1 diabetes within 12 weeks prior to randomization (4-6 weeks from screening) and express peak C-peptide ≥ 0.2 pmol/ml Subjects will be randomized to hyperbaric oxygen chamber (HBOC) group and to a non-intervention, control group. Both groups will be managed similarly by carbohydrate counting and basal bolus insulin administration, based on their interstitial glucose levels by glucose continuous glucose monitoring system (CGMS) and carbohydrate counting before meals. The intervention protocol includes 12 weeks of intensive management, and 12 weeks of follow up. During the intensive management period - for 12 weeks, the HBOC group will receive 100% oxygen at 2 ATA for 90 min with 5 min air breaks every 20 min at each session. Intensive management period includes 60 daily sessions, 5 days per week within 12 weeks, During the intensive management period - for 12 weeks, the control group will receive common practice managemnt. All will be instructed to inject insulin pre-meals according to carbs-counting, and CGMS. Insulin will be administered by subcutaneous continuous insulin infusion (SCII) or by pens with CLIPSULIN only, for accurate daily dose of insulin recording. Along the 24 weeks of the study several parameters will be assessed at pre-defined time points . 1. Immune system parameters will be assessed by blood levels of T-regulatory cells, diabetes auto-antibody and inflammatory cytokines. 2. Pancreatic β cells function will be evaluated by measurements of blood area under the curve (AUC) C-peptide, peak C-peptide, and basal proinsulin/c-peptide ratio. 3. glycemic control parameters will be evaluated by CGMS data regarding time spent in glycemic range, hypoglycemic and hyperglycemic ranges, total daily dose of insulin according to CLIPSULIN , and blood tests for glycated hemoglobin (HbA1c). 4. Microbiome changes will be assessed by stool samples. Expected significance: the study suggests a safe modality used clinically among adults and other paediatric conditions, for the possible solution of an unmet urgent medical need, studied successfully in an animal model. The study is designed to be powered to answer the question of efficacy, and in addition, addresses the mechanisms by which it may halt the progression of β cell destruction in new onset T1DM.