To compensate for this problem, "in vivo" experimentation allowed testing to occur in the original organism or environment. To bridge the dichotomy of benefits associated with both methodologies, "in situ" experimentation allowed the controlled aspects of "in vitro" to become coalesced with the natural environmental compositions of "in vivo" experimentation. In conservation of genetic resources, ""in situ" conservation" (also "on-site conservation") is the process of protecting an endangered plant or animal species in its natural habitat, as opposed to "ex situ" conservation (also "off-site conservation"). In chemistry, "in situ" typically means "in the reaction mixture." There are numerous situations in which chemical intermediates are synthesized "in situ" in various processes. This may be done because the species is unstable, and cannot be isolated, or simply out of convenience. Examples of the former include the Corey-Chaykovsky reagent and adrenochrome. In biomedical engineering, protein nanogels made by the in situ polymerization method provide a versatile platform for storage and release of therapeutic proteins. It has tremendous applications for cancer treatment, vaccination, diagnosis, regenerative medicine, and therapies for loss-of-function genetic diseases. In chemical engineering, "in situ" often refers to industrial plant "operations or procedures that are performed in place." For example, aged catalysts in industrial reactors may be regenerated in place ("in situ") without being removed from the reactors. In architecture and building, "in situ" refers to construction which is carried out at the building site using raw materials. Compare that with "prefabricated" construction, in which building components are made in a factory and then transported to the building site for assembly. For example, concrete slabs may be "in situ" (also "cast-in-place") or "prefabricated". In situ techniques are often more labour-intensive, and take longer, but the materials are cheaper, and the work is versatile and adaptable. "Prefabricated" techniques are usually much quicker, therefore saving money on labour costs, but factory-made parts can be expensive. They are also inflexible, and must often be designed on a grid, with all details fully calculated in advance. Finished units may require special handling due to excessive dimensions. The phrase may also refer to those assets which are present at or near a project site. In this case, it is used to designate the state of an unmodified sample taken from a given stockpile.