Most known particles have either 3 quarks (baryons) or a quark-antiquark pair (mesons). The pentaquark is defined as a subatomic particle consisting of 4 quarks and one antiquark. If the pentaquark exists, then it would be a breakthrough in our understanding of how quarks can be put together to form composite particles. However, while there were claims by several experiments around the world for a pentaquark (now called the Θ+), newer, higher-statistics experiments put in doubt some of the earlier data claiming evidence for the Θ+. With better exeriments, Jefferson Lab was able to test the hypothesis that earlier experiments might have found evidence for the Θ+ pentaquark. The new data give a null result for the existence of the Θ+. This is an example of the scientific process at work; claims of new particles must be reproducible in experiments with higher statistical precision. Jefferson Lab has played a crucial role in the search for new and exotic types of subatomic particles.