  The 3MdB (Mexican Million Models database) is a large database of
photoionization models for H II regions. The number of free parameters for the
models is close to 15, including the description of the ionizing Spectral
Energy Distribution (effective temperature, luminosity, surface gravity, for
different type of stellar atmosphere models) and the description of the ionized
gas (distance to the ionizing source, density, abundances of the most common
elements, dust). The outputs of the models are more than 70 emission line
intensities, the ionic fractions and temperatures. All the parameters and
outputs are included in the MySQL database, giving the possibility to the user
to search into the database for example for all the models that reproduce a
given set of observations.
