In this paper we present the prototype of a light-weight multi-spectral sensor which can be flown on a micro UAV and we discuss the promising results from two field tests which show the excellent potential for assessing plant health in agronomical research. We start out by illustrating the gap between airand space-based remote sensing (RS) on the one side and ground-based RS on the other. We highlight the need for (very) high resolution remote sensing offered by low altitude airborne platforms such as mini or micro UAVs (unmanned aerial vehicles). For this purpose, we first discuss the specific characteristics and requirements of typical applications requiring very high resolution RS. We then look into recent developments in light-weight UAV technologies and present the micro UAV which served as platform for the sensor development and tests at the University of Applied Sciences Northwestern Switzerland (FHNW). In the following section we provide a description and discussion of the MultiSpectralMicroSensor (MSMS), the prototype of a light-weight multispectral sensor developed at the FHNW. We further describe two field campaigns with two different types of UAV platforms and MS sensors and discuss the obtained results, which clearly demonstrate the excellent potential of very high-resolution micro UAV based remote sensing applications. * Corresponding author.