Monocrystalline solar cells are made from thin wafers of silicon, sliced from large crystals that have been grown under carefully controlled conditions. The cells are typically a few inches across, and a number of cells are laid out in a grid to create a panel. Relative to the other types they have a high efficiency, meaning you will get more electricity from a given area of panel - useful if you only have a limited area for mounting your panels, or want to keep the installation small for aesthetic reasons. However, growing large crystals of silicon is a difficult and very energy-intensive process, and so the production costs of this type of panel have historically been very high. Production methods have improved though, and prices have fallen a great deal over the years, partly driven by competition as other types of panel have been produced.