Present Simple is used in complex sentences in subordinate clause after WHILE, BEFORE, AFTER, AS SOON AS, TILL, UNTIL.

• I’ll stay there until they come.
• He’ll have a party after he passes all his exams.
• Millie will definitely read all those books while she is on holiday.
• Before I leave you we’ll drink one for the road.
• I’ll get hold of this mansion as soon as she dies.

In a complex sentence we use the Present Simple Tense in the if- and when-clause if the Future Tense was used in the main clause.

• If she comes it will be a big scandal.
• When I go shopping I shall buy some food.
• We’ll be late if we don’t hurry up.
• I’ll invite Jill to the party when I send her an e-mail message tomorrow morning.