Today is the Feast Day of St. Thomas the Apostle.
Here are a few facts about the famous Apostle.
The Catholic Encyclopedia has more detail.
Finally, here's where he gets his famous adjectival moniker, although he had been bolder once:
24Now Thomas, one of the Twelve, called the Twin, was not with them when Jesus came. 25So the other disciples told him, "We have seen the Lord." But he said to them, "Unless I see in his hands the mark of the nails, and place my finger into the mark of the nails, and place my hand into his side, I will never believe."
26Eight days later, his disciples were inside again, and Thomas was with them. Although the doors were locked, Jesus came and stood among them and said, "Peace be with you." 27Then he said to Thomas, "Put your finger here, and see my hands; and put out your hand, and place it in my side. Do not disbelieve, but believe." 28Thomas answered him, "My Lord and my God!" 29Jesus said to him, "Have you believed because you have seen me? Blessed are those who have not seen and yet have believed."
By the way: he is my patron saint.
St. Thomas the Apostle, pray for us.
[Update: As always, Drake over at the superb Catholic Point of View has magnificent artwork to commemorate the occasion. Today, it's a Caravaggio: The Incredulity of St. Thomas. You know the drill--just go.]