Despite the recognized importance of cloud microphysics for climate, there are only few and insufficient microphysical observations in the tropics. Among them are those performed during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE, e.g., Takahashi et al. 1995), measurements in tropical cumulonimbi during the Stratosphere-Troposphere Exchange Project (STEP, Knollenberg et al. 1993), preliminary studies over Northeast Brazil (Ceará Experiment, Costa et al. 2000), microphysical data collected during the Central Equatorial Pacific Experiment (CEPEX, Chen et al. 1997) and the campaign carried out during the Tropical Rainfall Measuring Mission / Large Scale Biosphere-Atmosphere Experiment in Amazonia (TRMM-LBA). Those observations generally revealed important peculiarities in the microphysical structure of tropical convective clouds. As a means to help filling this gap, a field campaign focusing on microphysical measurements over Northeast Brazil is planned for March and April 2002, in the middle of the region's rainy season, the so-called "Experimento de Microfísica de Nuvens / Experimento de Semeadura de Nuvens" (EMfiN! / ESN). The major instrumentation comprises an aircraft with sensors for pressure, temperaure, humidity, radiation, cloud condensation nuclei, liquid water content and distribution of cloud droplets, drizzle drops and raindrops, a second aircraft, equiped for cloud seeding, a band-X meteorological radar and radiosondes. The objectives of the experiment include determining major aerosol sources, characterizing the warm phase microphysics of clouds, investigating differences in the macro- and microstructures of precipitating and non-precipitating clouds and evaluating possibilities of weather modification programs over the region. Preliminary results from the EMfiN! / ESN will be presented first hand at the AMS Cloud Physics Conference.