Invitations for the royal wedding were mailed out last week, and loads more details about the impending nuptials are coming in, such as who will be attending the big event and what guests will be wearing! While rumors are swirling that wedding outfitter Bruce Oldfield will be designing Kate Middleton's gown, we now know for sure what attendees must wear to the Westminster Abbey wedding, as the dress code was printed on the invitations: "uniform, morning coat or lounge suit." Sounds stuffy and conventional, but this formal attire can actually be quite fun and even colorful. Check out some examples of each, plus info on the spectacular hats Middleton has requested!

 Queen Elizabeth II in "morning dress"

Typical "morning dress" is clothing that fits somewhere between ultra-formal and business wear. It is traditionally worn until 6 p.m., and for women, it usually includes a hat and, often, gloves. Mini-dresses are forbidden in this dress code and if pants are worn they must be accompanied by a coat. The Queen is well-known for this look—especially her bright coats and matching hats—as exhibited here. Her hands are covered and her blouse matches the flower atop her head. Nice attention to detail!

Kate Middleton wore this a blue printed coat and hat to a wedding in 2009.

The first lady wore a lemongrass Isabel Toledo coat over a matching shift dress with green gloves to the inaugural events in 2009.

These are, by definition, single-breasted coats where the front is cut away, leaving “tails” in the back. They were originally designed to make it easier for the wearer to ride a horse.

What a handsome dude. We love Kate Middleton's outfit here as well, but it may be too casual for the occasion.