It's a picture of cells actually growing and moving in cell culture.

这幅图是真实细胞,在细胞培养液中生长和运动的样子

耶鲁公开课 - 生物医学工程探索课程节选

So what I've said so far is, a particle moving in time from point to point can be represented by a graph, x versus t.

到目前为止,我说过,一个质点随时间的连续运动,可以用一幅x-t图来表示

耶鲁公开课 - 基础物理课程节选