Architectural engineering, also known as building engineering or architecture engineering, is a discipline that deals with the technological aspects and multi-disciplinary approach to planning, design, construction and operation of buildings, such as analysis and integrated design of environmental systems (energy conservation, HVAC, lighting, acoustics, vertical and horizontal transportation), structural systems, behavior and properties of building components and materials, and construction management. Architectural engineering, also known as building engineering or architecture engineering, is a discipline that deals with the technological aspects and multi-disciplinary approach to planning, design, construction and operation of buildings, such as analysis and integrated design of environmental systems (energy conservation, HVAC, lighting, acoustics, vertical and horizontal transportation), structural systems, behavior and properties of building components and materials, and construction management. From reduction of greenhouse gas emissions to the construction of resilient buildings, architectural engineers are at the forefront of addressing several major challenges of the 21st century. They apply the latest scientific knowledge and technologies to the design of buildings. Architectural engineering as a relatively new licensed profession emerged in the 20th century as a result of the rapid technological developments. Architectural engineers are at the forefront of two major historical opportunities that today's world is immersed in: (1) that of rapidly advancing computer-technology, and (2) the parallel revolution arising from the need to create a sustainable planet. Distinguished from architecture as an art of design, architectural Engineering, is the art and science of engineering and construction as practiced in respect of buildings. Structural engineering involves the analysis and design of the built environment (buildings, bridges, equipment supports, towers and walls). Those concentrating on buildings are sometimes informally referred to as 'building engineers'. Structural engineers require expertise in strength of materials, structural analysis, and in predicting structural load such as from weight of the building, occupants and contents, and extreme events such as wind, rain, ice, and seismic design of structures which is referred to as earthquake engineering. Architectural Engineers sometimes incorporate structural as one aspect of their designs; the structural discipline when practiced as a specialty works closely with architects and other engineering specialists. Mechanical engineering and electrical engineering engineers are specialists, commonly referred to as (Mechanical, Electrical and Plumbing) when engaged in the building design fields. Also known as 'building services engineering' in the United Kingdom, Canada and Australia. Mechanical engineers often design and oversee the heating, ventilation and air conditioning (HVAC), plumbing and rain gutter systems. Plumbing designers often include design specifications for simple active fire protection systems, but for more complicated projects, fire protection engineers are often separately retained. Electrical engineers are responsible for the building's power distribution, telecommunication, fire alarm, signalization, lightning protection and control systems, as well as lighting systems In many jurisdictions of the United States, the architectural engineer is a licensed engineering professional. Usually a graduate of an architectural engineering university program preparing students to perform whole-building design in competition with architect-engineer teams; or for practice in one of structural, mechanical or electrical fields of building design, but with an appreciation of integrated architectural requirements. Formal architectural engineering education, following the engineering model of earlier disciplines, developed in the late 19th century, and became widespread in the United States by the mid-20th century. With the establishment of a specific 'architectural engineering' NCEES Professional Engineering registration examination in the 1990s, and first offering in April 2003, architectural engineering became recognized as a distinct engineering discipline in the United States.