In my dreams, I still hear the cries when they left their parents.
A long unacknowledged heroine, Irene Sadler, has passed away at age 98:

The Nazis ordered a stop to normal social services, such as food and health care. Charged with warding off typhus and tuberculosis, Sendler had official permission to move freely in the ghetto. She convinced Jewish parents to let her hide their children. She used an ambulance to smuggle children in burlap sacks and coffins. A dog seated next to her would sometimes bark to drown out the children’s cries. She received aid from the Zegota, the Polish Council to Aid the Jews.

The children were given new names and false documents, and placed with Christian Polish families and at Christian religious establishments. Sendler wrote their real names on slips of paper that she hid in bottles underground, intending to retrieve them later.

The Gestapo arrested Sendler in 1943 and tortured her brutally, breaking her legs and feet with wooden clubs. She was sentenced to be executed, but she escaped after the Zegota bribed a guard. She remained in hiding until the end of the war, then dug up the bottles under the apple tree and tried to reunite the children with their families. Most of the families had perished, though some were placed with relatives around Europe. She was known within Poland, but she received little publicity in the West during the Cold War years. In 1980, she joined the Solidarity movement.