The image describes the mystery of the missing antimatter*. 

The centre illustrates the first instants after the Big Bang, when the temperature was so high that matter-antimatter creation and destruction are in perfect balance. 

As the universe expands and In the expanding universe, the temperature decreases and the creation of new particle-antiparticle pairs stops (dark red zone), while particles and antiparticles continue to destroy each other.

If the matter-antimatter symmetry was perfect, the universe today should contain nothing but radiation.  However,  a tiny fraction of matter survives, forming all stars and planets in the universe today. 

 What caused antimatter to vanish? The LHCb experiment at CERN studies tiny differences in the decays of particles called B-mesons and their antiparticle partners to explore what happened to the missing antimatter.

*Antimatter particles (red) are the mirror counterpart of matter particles (blue), with the same mass and opposite charge. Particles and antiparticles are always produced in pairs, if a sufficient amount of energy is present. When they meet, they destroy each other, leaving only radiation.