Hong Kong first formed in the Mesozoic Era, when magma close to the surface pushed upwards to form the mountains that make up the mountains of the peninsula and islands today. Along the way the pushed up some old formations sitting above them, and in a couple of random spots magma found some small exits and lava spread in small amounts. However, for the most part, Hong Kong is essentially a bunch of laccoliths and batholiths that were raised during the eras right around the time of the dinosaurs. Geologically, the bulk of the SAR is quite similar to Son Tra, right near Da Nang. Both are large granitic masses resulting from sub-surface magma, and both rise abruptly from the sea. Today evidence can be seen of both pre-existing sediments and limestones that got pushed up by the mountains, and of lava flows, but the vast majority is basement rock of a granite nature.
The people of Hong Kong date back a long time. Evidence has been found on Lantau Island of people living as far back as 30,000 years ago. The island and it's harbors and bays were used by fishermen for thousands of years, but the true history of Hong Kong lies with the Her Majesty's Royal Empire, the British.