Visualisation of a carbon nucleus. This image represents the nucleus of a carbon atom. The nucleus is made of twelve particles, called nucleons (six protons and six neutrons). Each nucleon is composed of three quarks surrounded by a quantum cloud of virtual particles. Protons have two 'up' quarks and one 'down' quark, neutrons have two 'down' and one 'up'. The nucleons are bound together by the strong nuclear force, the same force which binds the quarks together within each nucleon. The colours in the image reflect the three charges of the strong force; known as red, green and blue. Each nucleon has one quark of each colour" (charge)."