This paper discusses the variability in space and time of microclimate in exhibition rooms and the related impact on collections composed of organic materials. The main deterioration mechanisms and risk assessment tools are highlighted. The historic climate, recommended by the EU standard EN 15757:2010 to avoid mechanical damage for the conservation of organic hygroscopic materials is elucidated. The limits of tolerable temperature (T) and relative humidity (RH) variability on the long (seasonal) and short time-scale (fluctuations) are also presented. The uneven distribution of heat in a room, especially in the corners or behind furniture, creates a habitat favorable to mold infestation. Special temperature T and RH diagrams, produced under the EU funded “Climate for Culture” project, are useful to assess risk for infestation by insects and molds, as well as the risk of damage (deformation, cracking, or blistering) for wooden objects or polychromy. A discussion concerns the possibility of killing insects and molds with high or low temperatures, or using the vacuum cleaner. The lifetime of cellulose (paper and textiles) is also considered. The exhibition lighting is considered in light of two EU standards, i.e. CIE 157:2004 and CEN TS 16163: 2014. The standards provide useful recommendations about light sources, emission spectra, illuminance, and upper limit of annual luminous exposure for photosensitive surfaces. Finally, the paper presents the EU standard EN 15999-1: 2014 that is a guideline for design of showcases for exhibition and preservation of collections. It provides general instructions to reduce the risk of physical damage to exhibits (e.g. theft, vandalism, natural disasters) and to improve the control of environmental parameters (e.g. T, RH, dust, pollutants and light).