SUMMARYMicrometeorologyis the study of atmospheric processes at the earth's surface. If the leaves of plants and the skins of animals are regarded as extensions of that surface, micrometeorological principles can help the biologist to investigate the influence of physical environment on living material. Two examples are considered in illustration. First, the surface temperature of plants and animals and the cooling produced by evaporation are discussed in terms of heat‐balance equations. Second, it is shown that the uptake of carbon dioxide by a field crop can be measured by a micrometeorological techniqu