I personally love nanos and picos even more, but if you have never done saltwater or reef, keep this in mind: More water is more stable.
A pico such as that would require lots of regular maintenance. I do not mean that they would require a lot of time, but often. Keeping the water at a stable salinity is also tricky with this size tank. Water can evaporate fast and topping off the evaporated water can cause swings if not done properly. This will and limit many types of corals you can keep.
If you are bound and determined to start this small, check out the nano and pico forums. I have kept many, but giving all direction here is crazy.
Ask, Listen, and Learn before you start. Make sure you understand the nitrogen cycle, filtration methods, biological balance, and have a plan for animals you want to keep. Also, know what you can actually do as a maintenance schedule.
If you have ideas already, write them down and we can help you decide the right process to success.