The Assumption of Mary into Heaven
When Jesus died on the cross, he gave his mother to his apostle John. That means that he wanted Mary to treat John as her son, and John to treat Mary as his mother and take care of her. Mary moved into John's home, where he said Mass each day. So Mary was close to her Son in the Blessed Sacrament, even though He had ascended into Heaven.
Mary's love for God and Jesus grew even stronger than it had been when Jesus had been present on earth. She grew more holy every day. People came to visit her, she was kind and patient with everyone. Saint Luke (who wrote the Gospel of Saint Luke) painted a picture of her during this time. The portrait of 'Our Lady of Perpetual Help" which was painted centuries later, used Saint Luke's portrait as a model of what Mary looked like.
Finally when she was very old, it was time for Mary to die. She had enough time to say goodbye to all the apostles before she died. The grieving apostles took her body to a tomb near the one that Jesus was laid in. They covered her with a white shroud and laid her to rest in the tomb.
But Mary's body didn't stay there. Jesus came to her and took her body and soul into heaven to be with Him. Mary was the Immaculate Conception - the only person except Jesus who had been born without the stain of Original Sin,the disobedience of Adam and Eve. God and Jesus would not let the body of the Mother of God decay. This was her reward for her love of God and her years of faithful prayers and suffering.