Double fertilization -- WOAH

The angiosperm life cycle can be a bit tricky to learn, so let's break it down. Here's a pretty good diagram of the generalized process:

Following along by the numbers, let's start with the male anatomy:

1. So the anthers are where all the male material originates. Remember, sporangium is just tissue that holds spores (from Greek 'sporos' meaning ‘spore’ + 'angeion' meaning ‘vessel’), and when we see 'micro' it always refers to male reproductive cells (at least in the context of plant reproduction). So inside the anthers we find our microsporangium, which are at first holding diploid microsporocytes. These are our microspore mother (or father, to keep the male thing going) cells. 
2. These microsporocytes go through meiosis and we get 4 haploid microspores (i.e., male spores) from each microsporocyte. 
3. Each microspore develops (germinates) into a pollen grain (still haploid), each with a generative cell (where the sperm come from) and a tube cell. We can imagine a bee has now visited the flower and the pollen grains have stuck onto her legs, so let's leave them flying around for now, and move on to the 
4. Feminine side of things. Inside the ovary of the flower are the diploid ovules, which each have a megasporangium (sometimes called the nucellus) holding a megasporocyte, which is also diploid. 
5. Just like in the anthers with the microsporocytes, this megasporocyte (megaspore mother cell) goes through meiosis and we get 4 haploid megaspores (female spores). But, only one of these survives; the others are absorbed by the megasporangium. (Interestingly, it's the megaspore farthest from the micropyle that survives.)
6. This surviving megaspore germinates into the megagametophyte by dividing its nucleus mitotically, with the end result being 8 haploid nuclei. Cell walls form to make 7 different cells within the megagametophyte -- 
1. 3 antipodal cells that are at the chalazal end (opposite the micropyle) of the megagametophyte
2. 1 central cell containing 2 polar nuclei.
3. 2 synergids at the micropyle end of the megagametophyte, flanking the
4. 1 Egg cell.
7. Now let's go back to our pollen grains. The bee has now deposited the pollen grains on the stigma of another flower (let's pretend it's the flower our megagametophyte just formed in). The tube cell starts to digest its way down the style toward the ovary and ovules. It's basically digging a tunnel so that the sperm cells can enter the ovule.
8. The tube cell reaches the micropyle (opening) of an ovule and enters one of the two synergids. 
9. It then discharges two sperm cells (derived from the dividing of the pollen grain's generative cell) into the synergid.
10. One sperm cell fertilizes the egg cell to make a diploid zygote (which becomes the embryo), and the other fuses with the two polar nuclei in the central cell to form a triploid endosperm. (The actual ploidy of the endosperm varies widely among species, but we'll call it triploid here.) This is double fertilization -- one sperm cell fuses with the egg, another with the polar nuclei. This trait is a hallmark of the angiosperms!
11. The triploid endosperm serves as a food reserve for the developing diploid embryo. The integuments develop into the seed coat, and once the seed is mature (with cotyledons, radicle, etc.), it can
12. Germinate!