overnight, now upsettingly familiar crackle of gunfire for many in ukraine. the reality of life in a country at war sounding throughout the night. this is the quietest we've seen the centre of kyiv, and this is being replicated in cities across the country. ukraine's defense has been both surprising and extraordinary, but it is still the underdog and russia is still making gains. at the largest pediatric center in ukraine, staff are used to battling disease. now they have to adjust to war. doctors say they have enough supplies, but the world health organization warns if the situation gets worse, oxygen supplies could run out. outside, ill children wait with their worried mothers to be transferred to poland for cancer treatment no longer available here. this boy is facing a risky journey with his mother.