The concepts of laser‐plasma based accelerator and injector are discussed here. A two stage laser plasma accelerator design study for the production of a high‐quality GeV electron beam with low energy spread (1%) is proposed. New results demonstrating colliding laser pulse scheme will be also presented. These laser‐produced particle beams have a number of interesting properties and could lend themselves to applications in many fields, including medicine (radiotherapy), chemistry (radiolysis), accelerator physics. They could be used as a source for the production of γ ray beams for non‐destructive material inspection by radiography, or for future compact XFEL machines.