It's Ada Lovelace day, celebrating the work of women in mathematics, science, technology and engineering. To celebrate we bring you a selection of articles by female authors that were published on *Plus* this year (including those written by the entirely female *Plus* editorial staff). To find our more about the pioneering work of Ada Lovelace herself read our article Ada Lovelace - visions of today. You can also check out our Ada Lovelace day blogs from 2012 and 2011 for more by and about women mathematicians.

Do infinites exist in nature? — Marianne Freiberger and Rachel Thomas talk to physicists, philosophers and cosmologists in search of the unbounded.

The lost mathematicians: Numbers in the (not so) dark ages — Charlotte Mulcare asks what medieval mathematicians got up to and whether they left a useful legacy.

Let me take you down, cos we're going too ... quantum fields
— In this four-part series the *Plus* editors Marianne Freiberger and Rachel Thomas explore the dramatic history of quantum electrodynamics.

Cognition, brains and Riemann — Joselle DiNunzio Kehoe explores our perception of space, Riemann's geometry and parallels between the two.

Folding the future: From origami to engineering — Kim Krieger finds an unlikely connection between combinatorics, origami and engineering.

What is space? — Francesca Vidotto tells us how the existence of tiny black holes make it impossible to measure lengths shorter than a shortest scale.

Are there parallel universes?
— *Plus* editor Marianne Freiberger finds parallel worlds in the puzzling mathematics of quantum mechanics.

Is the Universe simple or complex? — Faye Kilburn asks biologists, physicists, mathematicians and philosophers for their idea of how the Universe is structured.