 A solderless breadboard is the natural choice to connect all those development and breakout boards you've been collecting. It's fast and easy to configure. But beginners often think breakout boards are solderless too, sometimes mounting them loosely on the short ends of the header, other times pinning the board down using the long ends. Mechanically speaking it is fairly stable, but electrically speaking it's not. Unless you're using boards with secure connectors like a STEMIQT or Grove, you do need to solder in those headers. Cut or snap your header down to match the number of pads on your board. Plug the long legs down into the breadboard. Place the breakout on top. Then solder all the pins. Now that's electrically connected.