The Compact Muon Solenoid CMS is one of the major detectors of the LHC Large Hadron Collider accelerator. The second, a competitive brother, is Atlas. The accelerator complex in CERN was shut down for two years, after two years of exploitation, and will resume its work in 2015. During this break, called long shutdown LS1 a number of complex components, including electronics and photonics, will be intensely refurbished. Not only the LHC itself but also the booster components and detectors. In particular, the beam luminosity will be doubled, as well as the colliding beam energy. This means tenfold increase in the integrated luminosity over a year to 250fb⁻¹y. Discovery potential will be increased. This potential will be used for subsequent two years, with essentially no breaks, till the LS2 in 2017. The paper presents an introduction to the research area of the LHC and chosen aspects of the CMS detector modernization. The Warsaw CMS Group is involved in CMS construction, commissioning, maintenance and refurbishment, in particular for algorithms and hardware of the muon trigger. The Group consists of members form the following local research institutions, academic and governmental: IFD-UW, NCBJ- Świerk and ISE-WEITI-PW.