Big Data technologies enable us to build the digital brain of smart systems. I will illustrate with examples how we build a digital brain by collecting data from a large number of sensors and using the brain to find value in that data. We build a Data Lake using cutting edge technology from Pivotal and use it to store large amounts of sensor and other data. Then we can find patterns in that data by applying the Data Science methodology using sophisticated machine learning and statistical algorithms customized to run on big data within the Data Lake. Armed with these patterns the system can detect anomalies and respond in an appropriate manner. Data Science combined with sensors and actuators can make a system smart!