Histological sections are cut from embedded tissues and placed on glass slides. This is done with a microtome. Paraffin blocks are cut with steel blades. Plastic embedded tissue blocks are cut with glass or diamond knife. Frozen sections prepared with a cryo-microtome are sometimes necessary either for rapid histopathological diagnostics or as an alternative to paraffin histology when for a number reasons special methods cannot be performed with the latter. When tissue sections will not adhere sufficiently strong to glass slides, adhesives are recommended. The most popular way to keep sections on slides is to coat them with polylysine (a basic polymer) or with APES (3-aminopropyltriethoxysilane).