Playing with numbers and counting

My 5 year old was in his room getting some small cars to take in the bathtub. I could hear him counting by 2's: 2, 4, 6. Then, he counted them by 1's: 1, 2, 3, 4, 5, 6. Suddenly he exclaimed, "Mom, it's the same number if you count by twos or count by ones." I didn't hear him totally clearly and wasn't sure if I understood exactly what he meant. He came out to me and said, "See Mom?" He proceeded to line up the cars and count them by two's, arriving at the total of six. Then he lined them back up again and counted by one's, again arriving at six. "Isn't that cool Mom? It's six if you count by two's or by one's." I love it when they make connections like that on their own.