  The morphological phase transition between a sessile and lenticular shapes of
a droplet placed in a nanochannel is observed upon increasing the droplet
volume. The phase diagram for this system is discussed within the macro- and
mesoscopic approaches. On the mesoscopic level, the van der Waals forces are
taken into account via the effective interface potential acting between the
channel walls and the droplet. We discuss the contact angle dependence on the
droplet volume and the distance between the walls; this angle turns out to be
smaller than the macroscopic Young's angle. The droplet presence induces the
solvation force acting between the channel walls. It can be both attractive and
repulsive, depending on the width of the channel.
