Email is one of those things that everyone has to deal with. While there are common issues like receiving too much spam mail and so on, there are more fundamental issues with emails and one of those is viewing emails on different devices. More specifically, different screen sizes and ratios. While this was (and in some cases, still is) an issue for websites in general, recently websites have adapted to its different viewing mediums. Which means viewing web materials on a desktop is quite a different experience to viewing the same content on a mobile. This is because content has now been optimized for mobile viewing. This is not strictly the case with emails though.
Which is why Google has today announced that Gmail will soon start supporting responsive design. If you are unfamiliar with the term, then as a very simplistic explanation – responsive design is designed to make sure that the experience of viewing content is directly relevant to the size of the device that it is being viewed on. While mobile websites make use of a whole different interface, responsive design makes sure that the same content is displayed more in line with the device that is being used.
So the basic takeaway here is that emails received (which make use of responsive design) and are viewed through Gmail will be better adapted to the size of the screen you are using. This includes aspects within the email like links, buttons and so on, which will all increase in size to be easier to view and interact with on smaller screens. It is also worth knowing that the process works both ways as well. As some emails and content is sent with mobile viewers primarily in mind, if you are viewing the content on a desktop, you will also notice improvements to the presentation of the content. At present Google has not specifically stated when the support for responsive design will go live, but does say that it will happen "starting later this month". In the meantime, you can see an example of what you can expect with the coming responsive design support in the image below.