Medics from Great Ormond Street Hospital in England are meeting two international experts and Charlie Gard's mother to discuss the 11-month-old's condition.
The meeting has been set up after Michio Hirano, a professor of neurology at the Columbia University Medical Centre in New York, spent around four-and-a-half hours inside the hospital on Monday.
He was given full access to Charlie's medical records and hospital and clinical facilities, including diagnostic images.
Dr Hirano was also given an opportunity to examine Charlie.
The identity of a second international expert is subject to media reporting restrictions.
The meeting on Tuesday is being attended by the team currently caring for Charlie, including a consultant paediatric intensivist, a consultant paediatric neurologist, a consultant in paediatric metabolic medicine, and a consultant neuroradiologist.
Charlie's mother, Connie Yates, is also attending, alongside an independent chairman.
A structure agreed by all parties is in place for the meeting, with key questions agreed by all parties.
All doctors and researchers in the meeting are bound by patient confidentiality.
Great Ormond Street said it would be for the court to decide next steps regarding Charlie.
Charlie's parents are fighting for the right to take the 11-month-old to the US for a therapy trial for his rare genetic condition, overseen by Dr Hirano.
Great Ormond Street Hospital specialists say that treatment will not work, and the little boy's life support should be turned off.
His parents, from Bedfont, west London, have already lost battles in the High Court, Court of Appeal and Supreme Court.
They also failed to persuade European Court of Human Rights judges to intervene.
Mr Justice Francis has considered the couple's latest claims at preliminary hearings in the Family Division of the High Court in London.
He is due to stage further hearings later this month following this week's meetings.