Shredded Wheat, basically what the word says, wheat wetted, shredded, formed and backed; comes in different sizes with different add-ons like sugar, honey etc.; normally served swimming in milk.
Is there a filled variation too?

Puffed wheat. Sorry for the foul joke about “puffed”. There is “Puff-Reis”, kind of blown-up-rice-crispy, comes in plain form or coated with chokolade, so I guess puffed wheat is made the same way. Never seen it, never heared about it before, of course never tasted it.

Oatmeal: Oat is “Hafer”, a Korn like Gerste, Weizen, Dinkel etc. It is horse-food normally, under some circumstances it is thinkable to be used for human nutrition, as in war-times; maybe “Haferpl├Ątzchen” / oatcookies are different. There may be other opinions. Oatmeal is cooked oat, that becomes slimy, hence the German name “Haferschleim”. That is served in hospitals in a salty variation – that induces that there is a sweet version too?

Grits: Unknown variation of unknown ingredients. Had a glance at wikipedia and it seems to be something of southern descent that gets nixtamalized.
[This is a very good example for my idea about “normal exotism” – what is a home-made translation for “Binnen-Exotismus”: Basically it says that the most exotic things are not to be found somewhere at the other end of the world (in a different and unknown cultural set of relations), but just here, where you are, in your and mine normality (in the parts of our “normal” cultural setting we just do not know or we are not conscious about), nixtamalized grits for example.]

Porridge: Remains a mystery. Years ago some scots re-cooked what was found in the stomach of a moore-corpse, it consisted of some old variety of Korn (DInkel), herbs and different things I do not remember – they summed it up as it would taste like their daily morning porridge. Does that mean that after having had porridge in the morning there is only the way to the bog left? Is it made from oat? What is in?

Muesli: Well … opinions differ on that. I do not want to go into the gruel details.

So we have wheat (Weizen), oat (Hafer), grit (Mais) – what leaves out only Gerste, barley as my dictionary says, Roggen, rye, and probably Dinkel, but I guess this is no longer cultivated – it had a kind of renaissance in Germany over the last years, it’s an old variety. From barley beer is made and rye gives a nice wiskey. But my breakfast changed over the years.
Some pictures would be nice!

Ceres is a very old goddess of agriculture, death and marriage. Very female. The Tusci knew here, the Greek (Demeter, Dionysos, Kore). The ethymology of her name leads to crescere (to grow), creare (to create) and cernere (to distinguish). So in a way you can start the day with some good thoughts and thanks to her when forking the wheat.