We use the Gerund after the following prepositions:
after	After having a shower, I waited for Steven.
before	The tablet must not be taken before getting up in the morning.
by	I manage it by working much longer than 40-hour weeks.
in spite of	In spite of studying a lot he didn't pass the exams.
on	She insisted on calling her sister.
without	He told the joke without laughing.