Biology is beautiful. Living organisms have symmetries, colours and shapes that are aesthetically pleasing. Our eyes can only appreciate this at centimeter or millimeter resolutions, but the same is true on much smaller scales. It's an obvious thing to say, but computers (and increasingly inexpensive data storage) have changed the way we can see biological events. Videos containing gigabites of high-resolution data are easy to generate, and can give us a four-dimensional view of development and other cellular processes. Erik Sahai's lab always showed beautiful videos of migrating cells during their seminars and it made me want to study migration. If you're a Youtube junkie like me, here are a couple of videos that are worth watching:
From a textbook publisher with some great videos including audio explanations of what you're seeing:
http://www.youtube.com/user/garlandscience#p/a (check out the zebrafish development video)
The development of the eye itself is a complex and multi-step process. It starts as a big ball of cells that then gets flattened into a bilayer called the optic cup. This bilayer is like taking the air out of a volleyball or soccer ball and pushing in one side until it's folded in half. The lens of the eye then sits at the opening of this bilayer. A fascinating new publication from Yoshiki Sasai's lab shows that these first few stages of eye development can happen in mouse embryonic stem cells growing ex vivo (i.e. in a dish). Naturally, there are also great videos of this process.
Differentiation of organs ex vivo is both a goal and a tool for developmental biologists. If organs such as the retina could be grown in dishes it would reduce the need for organ donations where demand always outstrips supply. It would also allow for custom organs to be grown, making organ rejection less likely. Growing organs ex vivo also marks an important point in our understanding of how that organ develops. A mouse (or any other organism) starts out as a single cell and ends up with many different kinds of cells including heart cells, lung cells, and muscle cells. Two identical cells side-by-side will grow and divide and change into very different cells by the time development is complete. Numerous signals from neighbouring cells and the rest of a cell's environment help to ensure that each cell chooses the correct fate for its time and place. To recapitulate this in a dish is no small feat. Luckily for early eye development, the requirements for differentiation are minimal and the optic cup develops spontaneously from balls of cells. Most organs will probably need a precisely engineered environment that will be defined over many years through trial and error, but the optic cup system is a good start.