How This Happens
From the Catechism of the Catholic Church, Simplified
Reunited with the Soul (997-998)
At death, the human body decays. The soul goes to meet God while awaiting reunion with the body. God will definitely grant incorruptible life to our bodies by reuniting them with our souls. All will rise: "Those who have done good to the resurrection of life, and those who have done evil to the resurrection of judgment" (Jn 5:29).
Those Blessed in Christ (999)
This gift comes from Christ who "will change our lowly body to be like his glorious body" (Phil 3:21). "The dead will be raised imperishable, for this mortal nature must put on immortality" (1 Cor 15:35-37).
By the Eucharist (1000)
Although the answers to how this actually happens is accessible only through faith, our sharing in the Eucharist gives us a foretaste. "Just as the bread is no longer ordinary bread but Eucharist, so too our bodies which partake of the Eucharist are no longer corruptible but possess the hope of resurrection" (St. Irenaeus).
At the End of Time (1001)
This will happen at "the end of the world" (the Last Day) because this resurrection is associated with Christ's Second Coming. "The Lord himself will descend from heaven and the dead in Christ will rise first" (1 Thess 4:16).
A Hidden Gift (1002-1003)
By Baptism, we have already risen with Christ. "You were buried with him in Baptism, in which you were also raised with him through faith" (Col 2:12). This life, however, is "hidden with Christ in God" (Col 3:3). The Father has already "raised us up with him" (Eph 2:6). We belong to Christ's Body and on the Last Day "will appear with him in glory" (Col 3:4).
Respect for the Body (1004)
Every believer's body and soul already share in Christ's dignity. Therefore, each believer must respect his own body and the bodies of others. "The body is meant for the Lord, and the Lord for the body" (1 Cor 6:13).