Recommended tools for graphs and charts I have seen a couple of images in several papers like those attached below. These images are really expressive also nice i.e. look very scientific. I have no idea how to generate such images since I have in the past used powerpoint/excel. I'd appreciate some pointers on the tools for generating such images or even better ones.

UPDATE Just to clarify about duplicated question(s), this question is quite specific to graphs like those that combine several features concisely into a line /bar graph or scatter plot e.t.c. (as provided in the attached images). Some similar questions e.g. this one is about illustrations as seen in the answers provided. I think my question is different, so are the answers provided different from those in the referenced question.
The R language has a number of libraries to produce clean looking graphs, for example ggplot2.

The example below was made with the galluvial extension for ggplot2, one of many extensions that allow animation, interactive graphs, and more.