Theano is an open-source Python library that enables efficient definition, optimization, and evaluation of mathematical expressions involving multi-dimensional arrays. Particularly favored in the field of machine learning, Theano integrates seamlessly with NumPy, utilizes the power of GPUs, and generates dynamically compiled C code for optimal performance. Originally developed by the LISA (now MILA) group at the University of Montreal, Theano has been instrumental in advancing deep learning research by providing a robust platform where computations can be expressed in a concise and precise manner. More about Theano and detailed documentation can be found on its official website at [deeplearning.net](http://www.deeplearning.net/).