Fact-packed, smart lyrics geared to older children and teens about photosynthesis, gravitational pull, the circulatory system--even lab safety--are sometimes overwhelmed by a sophisticated rap beat and rapid-fire vocals. Wisely, the tracks are repeated on CD 1 in slower, down tempo versions, while the same songs are also offered on CD 2 in two different ways: "recall tracks" with missing words to fill in and karaoke-style tracks for more challenging listener interaction.