Neural networks are computational methods inspired by biological neurons that learn patterns from data to improve climate models, analyze particle collisions, and study cellular behavior.Card by card, lion after lion, zebra after zebra — thousands of examples pass through the network. Each layer of artificial neurons extracts increasingly abstract features: first it catches edges and lines, then assembles them into parts of a face, then into a complete image. The final layer gives an answer — much like a child looks at ears, whiskers, and tail to say 'cat'.
The concept of an artificial neuron dates back to the work of Warren McCulloch and Walter Pitts (1943), who proposed a mathematical model of the neuron. In 1958, Frank Rosenblatt created the perceptron — the first trainable neural network. However, after criticism by Marvin Minsky and Seymour Papert in 1969, interest waned. Revival began in the 1980s with the development of multilayer networks and the backpropagation algorithm (David Rumelhart et al.). In the 2000s, the availability of big data and GPU computing led to deep learning.
The input signal passes through layers: each neuron computes a weighted sum of inputs, adds a bias, and applies a nonlinear activation function (ReLU, sigmoid, etc.). Training minimizes a loss function via gradient descent; gradients are computed by the backpropagation method — from output to input, using the chain rule of derivatives.
Face recognition in photos, voice assistants, weather forecasting.
In 2012, the AlexNet network surpassed humans for the first time in an image recognition competition — it became clear then: the era of deep learning had begun.




















