Development of lungs starts to  occur by age of 4 weeks. And it is completed by 8 years of life. 

The mnemonic is 

Every pulmonary can see alveoli.

E – Embryonic phase

P- Pseudoglandular phase

C- Canalicular phase

S- Saccular phase

A- Alveolar phase

Table showing Phases of growth of alveoli and their properties