I learned to appreciate really good coffee when I worked in Italy. Soon, I purchased my first espresso-machine, a Gaggia Milady. After a couple of years, I switched to the Gaggia Classic, still a single boiler machine. These machines are compact and use one boiler for brewing coffee and espresso, as well as for frothing milk.
Lately, I upgraded to a semi-professional heat exchanger espresso machine, the Bezzera BZ10. Such machine boasts a powerful, high-capacity boiler capable of brewing and steaming at the same time.
Luigi Bezzera is the inventor of the espresso machine, in the early 1900's.