This, my dear friends, is the product of 5.5 weeks of rigorous pipetting. You are looking at a sea urchin embryo (about 24 hours post-fertilization), which is about the size of a sand grain to the naked eye. This little guy is labeled for a gene called nodal, one of several genes involved with organizing the developing cells into body regions via several axes. I spent most of the past month making "probes," RNA constructs labeled with a fluorescent tag, so that I could use a (super sweet) confocal microscope to look at multiple layers of the embryo. Anywhere you see red, that means a cell in the urchin is expressing the gene we're interested in. The clumping in one place is a positive result (I may or may not have jumped around the microscope suite when I saw it...); these cells make up the "animal pole," which helps comprise the initial body axis.Isn't it pretty?!
