When a star is born, a protoplanetary discs, consisting of dust grains
and gas, forms around it. Inside this disc, the dust grains can start to
grow and form larger and larger objects until finally planetesimals –
objects of about 100km in size – are formed. These planetesimals can
then grow by further accreting other planetesimals or pebbles –
particles of mm to cm in size. These planetary embryos can then finally
start to accrete gas once they reach several Earth masses and transition
into a gas giant. This growth process covers several orders of magnitude
in size and many orders of magnitude in mass. Naturally there are many
unknowns in this process.

Observations of extra solar planets have revealed that so-called
super-Earths and mini-Neptunes are the most abundant class of planets in
the galaxy, where about every 3rd solar type star should host such a
planet. These planets can harbor a variety of composition going from
rocky to potentially water rich worlds. In this talk, I will review
current observations of exoplanetary systems and then discuss the
potential formation pathways of these planetary systems. In particular I
will focus on the formation of close-in super-Earths and mini-Neptunes.