Pentaquark

From BBC News - Behold the pentaquark :

Physicists have discovered a new class of subatomic particle that will provide unexpected insights into the fundamental building blocks of matter.The new particle is the so-called pentaquark - five quarks in formation. Until now, physicists had only seen quarks packed into two- or three-quark combinations.

Until recently, no firm evidence of pentaquarks existed, even though physicists have searched for these objects for over 30 years.