The London typography
The selected font for the London theme is Roboto, with a mechanical skeleton and largely geometric forms while featuring friendly and open curves. By allowing letters to be settled into their natural width, Roboto makes for a more natural reading rhythm more commonly found in serif types.
Heading 1
Heading 1 styles should only be used when you want to repeat the screen title style within your screen, so avoid using it unless you have a really good reason. 
Heading 2
The heading 2 should be used as a page-level heading and you can use more than one per screen, each one representing a screen section.
Heading 3
Use the heading 3 for each sub-section you want to add in your application, below a heading 2 section. 
Bold text
Use bold to emphasize words within a sentence but, just like italic, use them as little as possible as it makes the text harder to read. Like ALL CAPS, bold and italic are fine for short pieces of text but not for long ones. Also avoid their use for titles, as you can see they just don't work as well as the headings.
Italic text
Italic texts are typically used for quotations or to emphasize a word like bold. Again, use it as little as possible for the same reasons as the bold text.
Hyperlinks have the main color of your theme. They can be used for navigation or secondary actions which you do not want to highlight.
Underline should only be used for links. It's ugly and makes text harder to read, so avoid it.
Click here to see your activities