A complex sentence has one main sentence and one or more subordinate sentences. Subordinate sentences expand the main idea in a complex sentence. In fact, a complex sentence is like a growing family.
 
Follow the pictures given below and you may understand it better.

Simple sentence:
He was filling the beer mug.

 

Compound sentence:
He was reading the paper and she was watching TV.

 

Complex sentence:
He was reading the paper while she was watching TV.

Just like a family grows, a simple sentence can be developed into a compound sentence and then into a complex sentence or into a compound complex sentence.

A friend who came to see me gave a story book he had with him
to my daughter who was very friendly with visitors when
he heard about her interest in reading short stories.

Main clause:

A friend gave a book to my daughter

Adjective clauses describing nouns:

A friend who came to see me
A story book he had with him
My daughter who was very friendly with visitors

Adverb clause of time:

When he heard about her interest in reading short stories

Complex sentences with past perfect tense

From the practice lesson ‘Planting A Rose Cutting’, you can learn a complex sentence pattern in which Past Perfect Tense and Past Simple Tense are used. Look at the picture given below. The main action was filling the pot and the subordinate idea gives the time of the action.

Before you make a complex sentence, you must think about the sequence of actions you are going to mention in the sentence. Here two actions come one after the other. Both the actions belong to the past. One is before past and the other is past. Therefore you must change the tenses accordingly.

I filled the pot with the mixture after I had mixed the soil and the manure together.

In this sentence our attention is focused on the time of the action.
e.g. I filled the pot with the mixture WHEN?

If you want to express similar ideas, you can use this sentence pattern.

Pattern: S+V2+O+ after S+had+V3+O.

I filled the pot with the mixture,
after I had mixed the soil and the manure together.

 

If you want to focus your attention on the main action, you can change the places of the two sentences.

Pattern: After S+had+V3+O, S+V2+O.

After I had mixed the soil and the manure together, I filled
the pot with the mixture.

 

After planting your rose cutting, think about the things you did and say what you did using the sentences given below.

I planted a rose cutting a few minutes ago. This is how I did it.
First I mixed the soil and the manure together. After I had mixed
the soil and the manure together, I filled the pot with
the mixture.After I had filled the pot with the mixture,
I made a hole in the middle of the pot. After I had made a hole
in the middle of the pot, I planted the cutting in the hole in
the pot. After I had planted the cutting in the hole in the pot,
I covered the hole with some soil. After I had covered the hole
with some soil, I press the soil in the pot. After I had pressed
the soil in the pot, I watered the pot. After I had watered
the pot, I kept it in a shade.

 

Now, use the other sentence pattern where the main sentence comes first and say what you did a few minutes ago. Follow the picture and the sentences given here. Be careful to break the sentences in correct places.

I planted a rose cutting a few minutes ago. This is how I did it.
First I mixed the soil and the manure together. I filled the pot
with the mixture after I had mixed the soil and the manure
together. I made a hole in the middle of the pot after I had
filled the pot with the mixture. I planted the cutting in
the hole in the pot after I had made a hole in the middle of
the pot. I covered the hole with some soil after I had planted
the cutting in the hole in the pot. I press the soil in the pot
after I had covered the hole with some soil. I watered the pot
after I had pressed the soil in the pot. I kept the pot in
a shade after I had watered it.