To make your image responsive, add "image-responsive" class to your image element. It will make your image responsive, will always take dimensions of your container and will adjust according to it.

To make your responsive image circular add "image-round" class to it.

You can also have different sizes for your responsive images. use "image-small", "image-medium", "image-large" to make them of a certain size that they can be contained with. You can use it with circular images as well.